Reservoir Rock Mechanics Relative Permeability PDF

RESERVOIR ROCK MECHANICS RELATIVE PERMEABILITY 20TH July-3RD August 2019 l SCHOOL OF CHEMICAL & ENERGY ENGINEERING l FACULTY OF ENGINEERING SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 www.utm.my Innovative · Entrepreneurial · Global SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 Relati...

RESERVOIR ROCK MECHANICS RELATIVE PERMEABILITY 20TH July-3RD August 2019 l SCHOOL OF CHEMICAL & ENERGY ENGINEERING l FACULTY OF ENGINEERING SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 www.utm.my Innovative · Entrepreneurial · Global SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 Relative Permeability Relative permeability • Definition of relative permeability • Laboratory method of measuring relative permeabilities • Effect of wettability • Factors affecting relative permeability • Correlations • Averaging www.utm.my Innovative · Entrepreneurial · Global It is expected that students will be able to: • define relative permeability of rock to a particular fluid for multi-phase fluid flow system • draw relative permeability curves • describe relative permeability measurements using Steady State and Un-Steady State Flow techniques • explain the effect of rock wettability on relative permeabilities and draw the relevant graph • explain factors affecting relative permeability • estimate relative permeabilities using published correlations, such as Stone, Corey, and NPC. • calculate and draw curves for relative permeability. Definition Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Give the accurate definition of relative permeability.. • Determination of relative permeability in lab. Introduce the steady state and unsteady state methods, their strength and weaknesses. • Factors influencing relative perm Discuss the effect of wettability, drainage process, imbibition process and connate water. • Correlations Discuss and apply the correlations to estimate relative perm. SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Concept If two or more fluid flow through a porous media, each fluid will flow according to Darcy’s Law. kw A ∆p qw = µ ∆L ko A ∆p qo = µ ∆L kg A ∆p qg = µ ∆L Saturated with water, oil and gas Theory Relative Permeability vos = − ko  dPo dz − πo g   ds  µ  ds vws = − www.utm.my Innovative · Entrepreneurial · Global kw  dPw dz − πw g   ds  µ  ds ko = porosmedia effective permeability to oil kw = porosmedia effective permeability vgs = − kg  dPg dz   − πg g  µ  ds ds  vos = oil phase velocity vws = water phase velocity vgs = gas phase velocity to water kg = porosmedia effective permeability to gas dPo = oil phasepressuregradient ds dPw = water phasepressuregradient ds dPg = gas phasepressuregradient ds Theory Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Effective permeability is the ability of a porous media to flow a fluid in the presence of one or more other fluids. The effective permeability to the fluid depends on -the amount or saturation of that fluid in the porous media -Wettability characteristics of the porous media -Saturation history Theory Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Relative permeability The effective permeability is usually presented in term of relative permeability. Relative permeability is the ratio of the effective permeability to a base permeability. For example, The ratio of effective permeability compared to absolute permeability kr = keffective k absolute or, The ratio of effective permeability to the effective permeability of non-wetting phase at irreducible wetting phase saturation. kr = keffective knw@ Swir Relative Permeability Curve Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Effective permeability ka Sw 0.1 0.206 0.316 0.4 0.5 0.6 0.7 0.8 250 400 md Keffnw 200 118.7 64.9 44.2 25.1 8.8 3.7 0 Keffw 0 4.4 13.3 20.6 29.5 43.5 61.2 100 200 150 100 50 0 0 0.2 0.4 Keffnw 0.6 0.8 Keffw 1 Relative Permeability Curve Relative Permeability ka Sw 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Innovative · Entrepreneurial · Global kr = k effective wrt k absolute 400 md Keffnw 200 118.7 64.9 40 21 8.8 3.7 0 www.utm.my Keffw 0 4.4 13.3 20.6 29.5 43.5 61.2 100 keff/ka krnw krw 0.5 0 0.29675 0.011 0.16225 0.03325 0.1 0.0515 0.0525 0.07375 0.022 0.10875 0.00925 0.153 0 0.25 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.2 0.4 0.6 krnw krw 0.8 1 Relative Permeability Curve Relative Permeability Sw 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Keffnw 200 118.7 64.9 40 21 8.8 3.7 0 Keffw 0 4.4 13.3 20.6 29.5 43.5 61.2 100 keff/knw(Swir) krnw krw 1 0 0.5935 0.022 0.3245 0.0665 0.2 0.103 0.105 0.1475 0.044 0.2175 0.0185 0.306 0 0.5 www.utm.my Innovative · Entrepreneurial · Global k relative = k effective wrt knw(Swir) 1.2 1 0.8 0.6 0.4 0.2 0 0 0.5 krnw 1 Relative Permeability Curve Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Point 1 - on the wetting phase relative permeability curve shows that a small saturation of nonwetting phase will drastically reduced the relative permeability of the wetting phase (the nonwetting phase occupies the larger pore spaces, and it is in the large pore spaces that flow occurs with the least difficulty. Point 2 - on the nonwetting phase relative permeability curve shows that the nonwetting phase begins to flow at relatively low saturation of the nonwetting phase. The saturation of the oil at this point is called critical oil saturation Soc. Relative Permeability Curve Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Point 3 - on the wetting phase relative permeablity curve shows that the wetting phase will cease to flow at a relatively large saturation (the wetting phase preferentially occupies smaller pore space, where capillary forces are the greatest). The saturation of the water at this point is refered to as the irreducible water saturation Swir (ketepuan air tak terkurang) Point 4 - on the nonwetting phase relative permeability curve shows that, at low saturations of the wetting phase, change in the wetting phase saturation have only small effect on the magnitude of the nonwetting phase relative permeability curve ( at low saturations the wetting phase fluid occupies the small pore spaces which do not contribute materially to flow, and therefore changing the saturation in the small pore spaces has relatively small effect on the flow of the nonwetting phase). Relative Permeability Curve Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Write your own note on Gas-oil relative permeability curves Effect of Res. Parameters on kr Relative Permeability 2 reservoir parameters considered: 1. Saturation history drainage imbibition 2. Rock wettability water wet rock oil wet rock www.utm.my Innovative · Entrepreneurial · Global Effect of Res. Parameters on kr Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Saturation history 2 types of saturation history Drainage process - Porous rocks is initially saturated with wetting fluid. The wetting fluid was then displaced with non-wetting fluid. This process, displacement of wetting phase by non-wetting phase, is called drainage process. Example – A water-wet rock that was saturated with water. Oil is then injected into the rock and displacing the water. The oil was non-wetting relative to water. Imbibition process - Porous rocks is initially saturated with non-wetting fluid. The non-wetting fluid was then displaced with wetting fluid. This process, displacement of non-wetting phase by wetting phase, is called imbibition process. Example – An water-wet rock was saturated with oil. Water is then injected into the rock and displacing the oil. The oil was non-wetting relative to water. Effect of Res. Parameters on kr Relative Permeability Saturation history Hysteresis: refers to irreversibility or path dependence. Drainage relative permeability curve is higher than the imbibition curve for non-wetting phase. www.utm.my Innovative · Entrepreneurial · Global Effect of Res. Parameters on kr Relative Permeability Rock wettability Several important differences between oil-wet curves and water-wet curves are generlly noted: a. The water saturation at which oil and water permeabilities are equal (intersection point of curves) will generally be greater than 50% for water-wet system and less than 50% for oil-wet system. b. The connate water saturation for a water-wet system will generally be greater than 20%, whereas, for oil wet-systems, it will normally be less than 15%. c. The relative permeability to water at maximum water saturation (residual oil saturation) will be less than about 0.3 for a water-wet system, but will be greater than 0.5 for oil-wet systems. www.utm.my Innovative · Entrepreneurial · Global Relative Permeability Correlation Relative Permeability Two-phase relative permeability correlations There are several correlations, among them are: a. Wyllie and Gardner Correlation (1958) b. Torcaso and Wyllie Correlation (1958) c. Pirson's Correlation (1958) d. Corey's Method (1954) www.utm.my Innovative · Entrepreneurial · Global Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) These correlations use the effective phase saturation as the correlating parameter. S S = 1− S * S −S S = 1− S * o o w wc w wc wc So*, Sw*, S g* = Effective oil, water and gas saturation So, Sw, Sg = Oil, water and gas saturation Swc = Connate (irreducible) water saturation S = * g S g 1− S wc Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) a. Wyllie and Gardner Correlation (1958) Types of formation kro krw Unconsolidated sand, well sorted (1− S ) Unconsolidated sand, poorly sorted (1− S ) (1− S ) (S ) Cemented sandstone, oolitic limestone * (S ) 3 * w w * w 2 *1.5 w 2 (1− S * ) 2 (1− S* ) o 3 w * 3.5 o (S ) * o 4 Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) a. Wyllie and Gardner Correlation (1958) (cont.) Types of formation kro krg Unconsolidated sand, well sorted (S ) (1− S ) Unconsolidated sand, poorly sorted (S ) (1− S ) (1− S ) Cemented sandstone, oolitic limestone (S ) * * 3 o * o 3.5 o * o 3 * 2 o 4 *1.5 o (1− S ) (1− S ) * o 2 *2 o Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) a. Wyllie and Gardner Correlation (1958) (cont.) If one relative permeability is available System kr Oil-water system  S  k = (S ) − k 1 − S    * * rw w 2 w ro * w  S  k = (S ) − k 1 − S    * Gas-oil system * ro o o rg * o Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) b. Torcaso and Wyllie Correlation (1958) kro in a gas-oil system. kro is calculated from the measurements of krg.  (S ) k =k  (1− S ) (1− (S * 4 o ro rg * o 2 * o  ) ) 2 Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) c. Pirson's Correlation (1958) Process Imbibition Wetting phase k = (S ) S rw Nonwetting phase * 3 w w (k ) r nonwetting 1  S − S =  − 1− S − S      )[1−(S ) S w wc wc Drainage k = (S ) S rw * 3 w w (k ) r nonwetting 2 = (1− S * w nw * w 0.25 ] .0.5 w Relative Permeability Correlation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Two-phase relative permeability correlations (cont.) d. Corey's Method (1954) A simple mathematical expression for generating the relative permeability data for the oil-gas system. The approximation is good for drainage processes, i.e gas-displacing oil. k = (1− S ro ) * 4 g k = (S ) (2 − S rg * 3 * g g ) Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Example Generate the relative permeability data for an unconsolidated well-sorted sand by using the Wyllie and Gardner method. Assume the following critical saturation values: Soc = 0.3, Swc = 0.25, Sgc = 0.05 Solution Drainage oil-water system k = (1− S ) * ro w k = (S ) * rw w 3 3 Drainage oil-gas system k = (S ) * ro 3 k = (1− S ) * rg S = * o 3 o o S = * g S 1− S S o S −S S = 1− S * w wc w wc g 1− S wc wc Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Oil-water relative permeability k = (1− S ) * ro w k = (S ) * rw 3 w S = * g S Sw 0.25 0.31 0.37 0.45 0.52 0.60 0.67 0.70 Sw* 0.0000 0.0857 0.1607 0.2607 0.3607 0.4607 0.5607 0.6000 * 1− S Soc 0.30 Swc 0.25 Sgc 0.05 S = g o wc S 1− S S = * o w wc wc kro 0.8 krw 0.0000 0.0006 0.0042 0.0177 0.0469 0.0978 0.1763 0.2160 w wc 1.0 0.9 kro 1.000 0.764 0.591 0.404 0.261 0.157 0.085 0.064 S −S 1− S krw 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.0 0.2 0.4 0.6 Sw 0.8 Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Oil-gas relative permeability k = (1− S ) * rg 3 o Sg 0.05 0.11 0.16 0.22 0.29 0.36 0.42 0.45 k = (S ) * ro Soc Swc Sgc 0.30 0.25 0.05 So 0.7000 0.6429 0.5929 0.5262 0.4595 0.3929 0.3262 0.3000 So* 0.933 0.857 0.790 0.702 0.613 0.524 0.435 0.400 3 S = * g o S 1− S S = * g o wc S 1− S S = * o w wc S −S 1− S w wc 1.0 kro 0.9 krg 0.8 kro 0.813 0.630 0.494 0.345 0.230 0.144 0.082 0.064 krg 0.000 0.003 0.009 0.027 0.058 0.108 0.180 0.216 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.00 0.10 0.20 0.30 wc 0.40 Sg 0.50 Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Example Generate the relative permeability data for an unconsolidated well-sorted sand by using the Pirson's method for water-oil system. Assume the following critical saturation values: Soc = 0.3, Swc = 0.25, Sgc = 0.05 Solution Process Imbibition Wetting phase k = (S ) S rw Nonwetting phase * 3 w w (k ) r nonwetting   S − S  = 1− 1 − S − S     w wc wc Drainage k = (S ) S rw * 3 w w (k ) r nonwetting = (1− S * w 2 nw )[1−(S ) * w 0.25 S ] .0.5 w Relative Permeability www.utm.my Innovative · Entrepreneurial · Global S −S S = 1− S Oil-water relative permeability (assume oil-wet system) k = (S ) S rw * 3 w w (k ) Soc 0.30 Swc 0.25 Sgc 0.05 Sw 0.25 0.31 0.37 0.45 0.52 0.60 0.67 0.70 Sw* 0.0000 0.0857 0.1607 0.2607 0.3607 0.4607 0.5607 0.6000 r nonwetting [ = (1− S )1− (S ) * w * w 0.25 S * ] wc 1.0 Pirson's krw kro 0.000 1.000 0.009 0.763 0.020 0.658 0.045 0.535 0.085 0.424 0.143 0.325 0.226 0.237 0.266 0.205 0.9 krw kro 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.0 0.2 0.4 wc w .0.5 w w 0.6 0.8 Sw 1.0 Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Example Use Corey's approximation to generate the gas-oil relative permeability for a formation with connate water saturation 0.25. Solution k = (1− S ro ) * 4 g k = (S ) (2 − S rg * 3 * g g ) Relative Permeability Gas-oil relative permeability k = (1− S ro ) * 4 g k = (S rg Soc 0.30 Swc 0.25 Sgc 0.05 Sg 0.05 0.14 0.22 0.33 0.44 0.55 0.66 0.70 Sg* 0.0667 0.1905 0.2988 0.4433 0.5877 0.7321 0.8766 0.9333 kro 0.759 0.429 0.242 0.096 0.029 0.005 0.000 0.000 krg 0.001 0.013 0.045 0.136 0.287 0.498 0.757 0.867 * g www.utm.my Innovative · Entrepreneurial · Global S = ) (2 − S ) 3 S * g * g g 1− S wc 1.0 kro 0.9 krg 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 0.2 0.4 0.6 0.8 Sg 1 Relative Permeability www.utm.my Innovative · Entrepreneurial · Global NORMALIZATION AND AVERAGING • Results of relative permeability tests performed on several core samples of a reservoir rock often vary. • It is necessary to average the relative permeability data obtained on individual rock samples. • Prior to usage for oil recovery prediction, the relative permeability curves should first be normalized to remove the effect of different initial water and critical oil saturations. • The relative permeability can then be de-normalized and assigned to different regions of the reservoir based on the existing critical fluid saturation for each reservoir region. Relative Permeability www.utm.my Innovative · Entrepreneurial · Global • The most generally used method adjusts all data to reflect assigned end values, determines an average adjusted curve and finally constructs an average curve to reflect reservoir conditions. • These procedures are commonly described as normalizing and de-normalizing the relative permeability data. Relative Permeability www.utm.my Innovative · Entrepreneurial · Global For a water-oil system: Step 1. Select several values of Sw starting at Swc (column 1), and list the corresponding values of kro and krw in columns 2 and 3. Step 2. Calculate the normalized water saturation S*w for each set of relative permeability curves and list the calculated values in column 4 by using the following expression: where ; Soc =Critical oil saturation Swc = Connate water saturation S*w = Normalized water saturation Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Step 3. Calculate the normalized relative permeability for the oil phase at different water saturation by using the relation (column 5): where kro = relative permeability of oil at different Sw, (kro)Swc = relative permeability of oil at connate water saturation: kr*o = normalized relative permeability of oil. Step 4. Normalize the relative permeability of the water phase by applying the following expression and document results of the calculation in column 6. where (krw)Soc is the relative permeability of water at the critical oil saturation. Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Step 5. Using regular Cartesian coordinate, plot the normalized kro* and krw* versus Sw* for all core samples on the same graph. Step 6. Determine the average normalized relative permeability values for oil and water as a function of the normalized water saturation by select arbitrary values of Sw* and calculate the average of kro* and krw* by applying the following relationships: and where n = total number of core samples, hi = thickness of sample i, ki = absolute permeability of sample i. Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Step 7. The last step in this methodology involves de-normalizing the average curve to reflect actual reservoir and conditions of Swc and Soc. These parameters are the most critical part of the methodology and, therefore, a major effort should be spent in determining representative values. The Swc and Soc are usually determined by averaging the core data, log analysis, or correlations, versus graphs, such as: (kro)Swc vs. Swc, (krw)Soc vs. Soc, and Soc vs. Swc which should be constructed to determine if a significant correlation exists. Often, plots of Swc and Sor versus log (k/Ф)0.5 may demonstrate a reliable correlation to determine end-point saturations as shown schematically in Figure 5-8. When representative end values have been estimated, it is again convenient to perform the denormalization calculations in a tabular form as illustrated below: Relative Permeability www.utm.my Innovative · Entrepreneurial · Global where (kro)Swc and (krw)Soc are the average relative permeability of oil and water at connate water and critical oil, respectively, and given by: Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Relative Permeability www.utm.my Innovative · Entrepreneurial · Global Relative Permeability www.utm.my Innovative · Entrepreneurial · Global RESERVOIR ROCK MECHANICS SATURATION 20TH July-3RD August 2019 l SCHOOL OF CHEMICAL & ENERGY ENGINEERING l FACULTY OF ENGINEERING SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 www.utm.my Innovative · Entrepreneurial · Global Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Fluid Saturation • Expected saturation values • Saturation from laboratory measurements It is expected that students will be able to: • define saturation of fluids in porous rocks • calculate saturation • explain saturation measurement using Retort, Soxhlet Extractor and calculate the saturation values Definition Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global What is fluid saturations in porous rock? Laboratory methods saturation determination Explain and calculate saturation values from Retort and Soxhlex Extractor Application of saturation data Examples on the use of saturation reservoir engineering calculations Definition Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Generally, a hydrocarbon formation was initially filled with water. Hydrocarbon migrated into the formation and filled fraction of he void spaces that were initially filled by water. As a result the formation is now filled with water and hydrocarbon, and the quantity of each fluid must be determined. Definition Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Fluid saturation in a porous media is a fraction of the fluid in the pore spaces of the rock. If V w = water volumein thepore V p = volumeof pore The water saturation in the poreis given by, V Sw = w Vp S w = water satiration in fraction or Sw = Vw *100 Vp % S w = water saturation in percent Methods to determine saturation Fluid Saturations Many methods are available, only 3 will be discussed: 1. 2. 3. Retort Distillation Method Solvent extraction (Soxhlet Extractor and Dean-Stark) Centrifugal Method www.utm.my Innovative · Entrepreneurial · Global Fluid Saturations 1. www.utm.my Innovative · Entrepreneurial · Global Retort Distillation Method Increase temperature up to 1000 - 2000 0F Water of crystallization Interstitial water www.utm.my Innovative · Entrepreneurial · Global Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global 2. Solvent extraction (Soxhlet Extractor and Dean-Stark) Extract until there is no more increment of water collected Sw = Vw Vp Sw = water saturation in fraction So = weight of saturated core (gm) - weight of dried core (gm) - weight of water (gm) oil density (gm/cc) * volume of pore(cc) So = oil saturation in fraction Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global 3. Centrifugal Method Solvent tube Core plugs A solvent is injected into the centrifuge just off center. Owing to centrifugal force it is thrown to the outer radii, being forced to pass through the core sample. The solvent remove the water and oil from the core. The outlet fluid is trapped, and the quantity of water in the core is measured. Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Factors affecting fluid saturations of cores Fluid content from the core sample (core taken from field) has change from its original content in the reservoir. a. Coring in the formation is influenced by drilling fluid invasion during drilling b. Bringing the core sample to the surface will cause pressure decline and the expansion of water, oil and gas Use of saturation data from lab Fluid Saturations 1. Determination of oil-water contact www.utm.my Innovative · Entrepreneurial · Global Use of saturation data from lab. Fluid Saturations 1. Determination of oil volume. Initial oil in-place N = 7758* A* h *ϕ *(1− Swi ) / Boi Sw = water saturation, fraction A = area of formation, acres h = tickness of formation, kaki ϕ = porosity, fraction Boi = oil formation volume factor, bbl/STB N = initial oil in-place, STB 7758 = bbl/(acre-foot) www.utm.my Innovative · Entrepreneurial · Global Several terms on saturation Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Connate water (Swc): water entraped in the intertices of the rock (either sedimentary or extrusive igneous) at the time the rock was deposited. Interstitial water : Water that occurs naturally within the pores of rock. Water from fluids introduced to a formation through drilling or other interference, such as mud and seawater, does not constitute interstitial water. Interstitial water, or formation water, might not have been the water present when the rock originally formed. In contrast, connate water is the water trapped in the pores of a rock during its formation, also called fossil water. Several terms on saturation Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Irreducible water saturation (Swir): the fraction of pore volume occupied by water in a resevoir at maximum hydrocarbon saturation. In water-wet rock, it represents the layer of adsorbed water coating solid surfaces and the pendular grain contacts and at pore throaths. The irreducible saturation of a fluid is the minimum saturation of that fluid attainable when that fluid is displaced from a porous medium by another fluid immmiscible with the first. The lowest water saturation, that can be achieved in a core plug by displacing the water by oil or gas. The state is usually achieved by flowing oil or gas through a water-saturated sample, or spinning it in a centrifuge to displace the water with oil or gas. The term is somewhat imprecise because the irreducible water saturation is dependent on the final drive pressure (when flowing oil or gas) or the maximum speed of rotation (in a centrifuge). The related term connate water saturation is the lowest water saturation found in situ. Residual oil (Sor): Oil remaining in the reservoir rock after the flushing or invasion process, or at the end of a specific recovery process or escape process. Several terms on saturation Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Several terms on saturation Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Several terms on saturation Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Saturation averaging Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Saturation averaging Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global www.utm.my Innovative · Entrepreneurial · Global Saturation averaging Fluid Saturations www.utm.my Innovative · Entrepreneurial · Global Example 4-3 Calculate average oil and connate water saturation from the following measurements: Sample 1 2 3 4 5 6 hi, ft 1 1.5 1 2 2.1 1.1 Soavg Swcavg ϕ, % 10 12 11 13 14 10 76.34915 23.65085 So, % 75 77 79 74 78 75 Swc, % 25 23 21 26 22 25 h*ϕ 10 18 11 26 29.4 11 105.4 h*ϕ*So h*ϕ*Swc 750 1386 869 1924 2293.2 825 8047.2 250 414 231 676 646.8 275 2492.8 RESERVOIR ROCK MECHANICS BOUNDARY TENSION & WETTABILITY 20TH July-3RD August 2019 l SCHOOL OF CHEMICAL & ENERGY ENGINEERING l FACULTY OF ENGINEERING SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 www.utm.my Innovative · Entrepreneurial · Global www.utm.my Innovative · Entrepreneurial · Global BOUNDARY (INTERFACIAL) TENSION Boundary Tension www.utm.my Innovative · Entrepreneurial · Global Interfacial (boundary) tension is the energy per unit area (force per unit distance) at the surface between phases. Commonly expressed in milli-Newtons/meter (also, dynes/cm). Surface tension = liquid and gas phase Interfacial tension = liquid & liquid phase (immiscible contact) Interfacial tension www.utm.my Innovative · Entrepreneurial · Global Interfacial tension exist when two phase are present. It is the force that holds the surface of a particular phase together and is a function of pressure, temperature and the composition of each phase. The tension of a water-hydrocarbon system varies from approximately 72 dynes/cm for water/gas system, 20 to 40 dynes/cm for water/oil system at atmospheric conditions. www.utm.my Innovative · Entrepreneurial · Global αgw = surface tension between gas and water αgo = surface tension between gas and oil αwo = interfacial tension between water and oil αws = interfacial tension between water and solid αos = interfacial tension between oil and solid αgs = interfacial tension between gas and solid Measurement www.utm.my Innovative · Entrepreneurial · Global There are various methods to measure surface tension of a liquid. One of the method consists of a platinum ring placed over the surface of liquid. Measuring the force required to separate the ring from the surface by over coming the surface tension of the water adhered to the ring as it is lifted. How Its Relate www.utm.my Innovative · Entrepreneurial · Global www.utm.my Innovative · Entrepreneurial · Global WETTABILITY SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 Wettability Definition www.utm.my Innovative · Entrepreneurial · Global Wettability is the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids. Wettability refers to interaction between fluid and solid phases. • Reservoir rocks (sandstone, limestone, dolomite, etc.) are the solid surfaces • Oil, water, and/or gas are the fluids www.utm.my Innovative · Entrepreneurial · Global Why Study Wettability www.utm.my Innovative · Entrepreneurial · Global Understand physical and chemical interactions between • Individual fluids and reservoir rocks • Different fluids with in a reservoir • Individual fluids and reservoir rocks when multiple fluids are presence Petroleum reservoirs commonly have 2 – 3 fluids (multiphase systems) When 2 or more fluids are present, there are at least 3 sets of forces acting on the fluids and affecting hydrocarbon recovery Wetting Fluid www.utm.my Innovative · Entrepreneurial · Global • Wetting phase fluid preferentially wets the solid rock surface. • Attractive forces between rock and fluid draw the wetting phase into small pores. • Wetting phase fluid often has low mobile. • Attractive forces limit reduction in wetting phase saturation to an irreducible value (irreducible wetting phase saturation). • Many hydrocarbon reservoirs are either totally or partially water-wet. Non Wetting www.utm.my Innovative · Entrepreneurial · Global • Nonwetting phase does not preferentially wet the solid rock surface. • Repulsive forces between rock and fluid cause nonwetting phase to occupy largest pores. • Nonwetting phase fluid is often the most mobile fluid, especially at large nonwetting phase saturations. • Natural gas is never the wetting phase in hydrocarbon reservoirs Adhesion Tension www.utm.my Innovative · Entrepreneurial · Global Adhesion tension is expressed as the difference between two solid-fluid interfacial tensions. Contact Angle www.utm.my Innovative · Entrepreneurial · Global The contact angle, θ, measured through the denser liquid phase, defines which fluid wets the solid surface. Oil Oil θ αos αow Water Oil αws αos AT = adhesion tension (milli-Newtons/m or dynes/cm) θ = contact angle between the oil/water/solid interface measured through the water (degrees) αos = interfacial energy between the oil and solid (milli-Newtons/m or dynes/cm) αws = interfacial energy between the water and solid (milli-Newtons/m or dynes/cm) αow = interfacial tension between the oil and water (milli-Newtons/m or dynes/cm ) Water Wet www.utm.my Innovative · Entrepreneurial · Global Water θ ΧΤos ΧΤws ΧΤws > ΧΤos ΧΤow Solid Oil ΧΤos 0° < θ < 90° If θ is close to 0°, the rock is considered to be “strongly water-wet” Oil Wet www.utm.my Innovative · Entrepreneurial · Global Water αos αos > αws θ αws αow Oil αos 90° < θ < 180° If θ is close to 180°, the rock is considered to be “strongly oil-wet” www.utm.my Innovative · Entrepreneurial · Global www.utm.my Innovative · Entrepreneurial · Global OIL-WET WATER-WET OIL Air θ θ FREE WATER θ < 90° θ OIL Oil WATER SOLID (ROCK) GRAIN BOUND WATER WATER WATER OIL OIL RIM θ > 90° θ WATER SOLID (ROCK) GRAIN FREE WATER Wettability Classification www.utm.my Innovative · Entrepreneurial · Global Strongly oil- or water-wetting Neutral wettability • No preferential wettability to either water or oil in the pores. Fractional wettability • Reservoir that has local areas that are strongly oil-wet, whereas most of the reservoir is strongly water-wet. • Occurs where reservoir rock have variable mineral composition and surface chemistry. Mixed wettability • Smaller pores area water-wet are filled with water, whereas larger pores are oil-wet and filled with oil. • Residual oil saturation is low. • Occurs where oil with polar organic compounds invades a water-wet rock saturated with brine. MEASUREMENT Most common measurement techniques • Contact angle measurement method • Amott method • United States Bureau of Mines (USBM) Method www.utm.my Innovative · Entrepreneurial · Global RESERVOIR ROCK MECHANICS CAPILLARY PRESSURE 20TH July-3RD August 2019 l SCHOOL OF CHEMICAL & ENERGY ENGINEERING l FACULTY OF ENGINEERING SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 www.utm.my Innovative · Entrepreneurial · Global SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 Introduction www.utm.my Innovative · Entrepreneurial · Global • Capillary pressure is important in reservoir engineering because it is a major factor controlling the fluid distributions in a reservoir rock. • Observable in the presence of two immiscible fluids in contact with each other in capillary-like tubes. • The small pores in a reservoir rock are similar to capillary tubes and they usually containing two immiscible fluid phases in contact with each other. • This interface arises from two immiscible fluid cause by interfacial tension effects. • In the presence of two immiscible fluids, one of them preferentially wets the tube surface and it is called the “wetting” fluid, the other fluid is the “non-wetting” fluid. www.utm.my Innovative · Entrepreneurial · Global The pressure difference existing across the interface separating two immiscible fluids in capillaries (e.g. porous media). Pc = pnwt - pwt Where: Pc = capillary pressure Pnwt = pressure in nonwetting phase pwt = pressure in wetting phase One fluid wets the surfaces of the formation rock (wetting phase) in preference to the other (non-wetting phase). Gas is always the non-wetting phase in both oilgas and water-gas systems. Oil is often the non-wetting phase in water-oil systems. Air / Water System ∆ h θ www.utm.my Innovative · Entrepreneurial · Global Air Water • Considering the porous media as a collection of capillary tubes provides useful insights into how fluids behave in the reservoir pore spaces. • Water rises in a capillary tube placed in a beaker of water, similar to water (the wetting phase) filling small pores leaving larger pores to non-wetting phases of reservoir rock. www.utm.my Innovative · Entrepreneurial · Global The height of water in a capillary tube is a function of: • Adhesion tension between the air and water • Radius of the tube • Density difference between fluids 2 αaw cosθ 1′h = r g 1′πaw This relation can be derived from balancing the upward force due to adhesion tension and downward forces due to the weight of the fluid (see ABW pg 135). The wetting phase (water) rise will be larger in small capillaries. Height of water rise in capillary tube, cm Interfacial tension between air and water, αaw dynes/cm = Air/water contact angle, degrees θ r = Radius of capillary tube, cm g = Acceleration due to gravity, 980 cm/sec2 Density difference between water and air, gm/cm3 1′πaw = Contact angle, θ, is measured through the more dense phase (water in this case). 1′h = = www.utm.my Innovative · Entrepreneurial · Global 1 2 AIR WATER 3 4 www.utm.my Innovative · Entrepreneurial · Global 1′h pa1 pw1 Air pa2 pw2 Water Water rise in capillary tube depends on the density difference of fluids. Pa2 = pw2 = p2 pa1 = p2 - πa g 1′h pw1 = p2 - πw g 1′h Pc = pa1 - pw1 = πw g 1′h - πa g 1′h = 1′π g 1′h www.utm.my Innovative · Entrepreneurial · Global • Combining the two relations results in the following expression for capillary tubes: 2 χρaw cos θ Pc = r Oil/Water System www.utm.my Innovative · Entrepreneurial · Global From a similar derivation, the equation for capillary pressure for an oil/water system is 2 χρow cos θ Pc = r Pc = Capillary pressure between oil and water χρow = Interfacial tension between oil and water, dyne/cm θ = Oil/water contact angle, degrees r = Radius of capillary tube, cm www.utm.my Innovative · Entrepreneurial · Global DRAINAGE Drainage Pd Mobility of nonwetting fluid phase increases as nonwetting phase saturation increases • Fluid flow process in which the saturation of the wetting phase increases • Mobility of wetting phase increases wetting phase saturation increases as Si = irreducible wetting phase saturation Sm 0.5 Swt • Four Primary Parameters Imbibition 0 Fluid flow process in which the saturation of the nonwetting phase increases IMBIBITION Pc Si • Sm = 1 - residual non-wetting phase saturation 1.0 Pd = displacement pressure, the pressure required to force non-wetting fluid into largest pores λ = pore size distribution index; determines shape Drainage Drainage Fluid flow process in which the saturation of the nonwetting phase increases. Examples: Hydrocarbon (oil or gas) filling the pore space and displacing the original water of deposition in water-wet rock Waterflooding an oil reservoir in which the reservoir is oil wet Gas injection in an oil or water wet oil reservoir Pressure maintenance or gas cycling by gas injection in a retrograde condensate reservoir Evolution of a secondary gas cap as reservoir pressure decreases www.utm.my Innovative · Entrepreneurial · Global Imbibition Process Imbibition • Fluid flow process in which the saturation of the wetting phase increases. • Mobility of wetting phase increases as wetting phase saturation increases. Examples: Accumulation of oil in an oil wet reservoir. Waterflooding an oil reservoir in which the reservoir is water wet. Accumulation of condensate as pressure decreases in a dew point reservoir. www.utm.my Innovative · Entrepreneurial · Global Pc vs. Sw Function Reflect to reservoir quality www.utm.my Innovative · Entrepreneurial · Global Permeability Effect www.utm.my Innovative · Entrepreneurial · Global 20 Capillary Pressure 16 Decreasing Permeability, Decreasing λ 12 C B A 8 4 0 0 0.2 0.4 0.6 Water Saturation 0.8 1.0 Capillary pressure, psia Grain Size Distribution Well-sorted Poorly sorted Decreasing λ Water saturation, % www.utm.my Innovative · Entrepreneurial · Global www.utm.my Innovative · Entrepreneurial · Global RESERVOIR ROCK MECHANICS FORMATION EVALUATION 20TH July-3RD August 2019 l SCHOOL OF CHEMICAL & ENERGY ENGINEERING l FACULTY OF ENGINEERING SUMMER SCHOOL: OIL & GAS LEARNING EXPERIENCE 2019 www.utm.my Innovative · Entrepreneurial · Global Petroleum System www.utm.my Innovative · Entrepreneurial · Global Petroleum Exploration - Geophysical www.utm.my Innovative · Entrepreneurial · Global • The application of the principles of physics to the study of the subsurface, in search of hydrocarbon • Geophysical investigations of the interior of the earth involves taking measurements at or near earth’s surface that are influenced by the internal distribution of physical properties. • The objective of any exploration venture is to find new volumes of hydrocarbons at a low cost and in a short period of time. • There are three main geophysical methods used in petroleum exploration: Magnetic, gravity and seismic. • The first two of these methods are used only in the predrilling phase. Seismic surveying is used in both exploration and development phases. Geophysical methods www.utm.my Innovative · Entrepreneurial · Global Method Measured parameter ‘‘Operative’’ physical property Gravity Spatial variations in the strength of the gravitational field of the Earth Density Magnetic Spatial variations in the strength of the geomagnetic field Magnetic susceptibility and remanence Electromagnetic (Sea Bed Logging) Response to Electric conductivity/resistivity electromagnetic radiation and inductance Seismic Travel times of reflected/refracted seismic waves Seismic velocity (and density) Seismic Geophysical Survey www.utm.my Innovative · Entrepreneurial · Global • • • • • The seismic methods are the most widely used of all geophysical methods used in petroleum exploration. Seismic methods measure seismic velocity of rock layers to detect both lateral and depth variations and the objective is to determine the lithology and geometry of the layers. A seismic wave can be thought of as shock wave (elastic wave) or vibration traveling through the ground. The rate of travel, or velocity, of the wave is related to the density of the rock. There are two types of elastic waves produced: 1) P-waves, which are primary or “compressional” waves, and 2) S-waves, or shear waves Seismic Survey www.utm.my Innovative · Entrepreneurial · Global The seismic method showing sound impulse bouncing off subsurface rock layer Type of seismic survey www.utm.my Innovative · Entrepreneurial · Global 2-D seismic survey 3-D seismic survey 4-D seismic survey 2-D seismic survey www.utm.my Innovative · Entrepreneurial · Global 2-D seismic survey 2-D Seismic Survey Advantages Disadvantages Easiest survey method Not effective in some location Inexpensive Anomalies are harder to map Not of better quality Exploration drilling success rate using 2D is very less (25%) www.utm.my Innovative · Entrepreneurial · Global 3-D seismic survey www.utm.my Innovative · Entrepreneurial · Global 4-D seismic survey www.utm.my Innovative · Entrepreneurial · Global 3-D 4-D Time 4-D seismic survey www.utm.my Innovative · Entrepreneurial · Global Helps geologist to understand how the reservoir reacts to gas injection or water flooding BENEFITS! Image Quality www.utm.my Innovative · Entrepreneurial · Global Economic analysis www.utm.my Innovative · Entrepreneurial · Global Formation Evaluation www.utm.my Innovative · Entrepreneurial · Global WHAT? • Formation Evaluation (FE) is the process of interpreting a combination of measurements taken inside a wellbore to detect and quantify oil and gas reserves in the rock adjacent to the well. • FE data can be gathered with wireline logging instruments or logging-while-drilling tools . • Study of the physical properties of rocks and the fluids contained within them. • Data are organized and interpreted by depth and represented on a graph called a log (a record of information about the formations through which a well has been drilled). Formation Evaluation www.utm.my Innovative · Entrepreneurial · Global WHY? • To evaluate hydrocarbons reservoirs and predict oil recovery. • To provide the reservoir engineers with the formation’s geological and physical parameters necessary for the construction of a fluidflow model of the reservoir. • Measurement of in situ formation fluid pressure and acquisition of formation fluid samples. • In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Type of formation evaluation www.utm.my Innovative · Entrepreneurial · Global Coring Well Logging Well Testing Coring www.utm.my Innovative · Entrepreneurial · Global • A cylindrical sample of rock obtained with a hollow drill is known as core • The sample us the analyzed for determining different petrophysical properties Coring www.utm.my Innovative · Entrepreneurial · Global Capillary pressure data Permeability information Objective Data for refining log calculations Reserves estimate www.utm.my Innovative · Entrepreneurial · Global Bottom hole coring Side wall coring Types of coring Bottom hole coring www.utm.my Innovative · Entrepreneurial · Global • The coring at the time of drilling is known as bottom hole coring • In the technique special bit is attached to BHA, hollow from inside. When drilling progresses core is being drilled and drill string is pulled out to obtain core. Wireline retrievable coring Conventional coring Type of bottom hole coring Conventional coring www.utm.my Innovative · Entrepreneurial · Global • The entire drill string is pulled to retrieve the core Advantage Large core can be obtained • 3 to 5 inch diameter • 30 to 55 ft long Disadvantage Time consuming Un-economical Wireline retrievable coring www.utm.my Innovative · Entrepreneurial · Global • In this method core and inner barrel are retrieved without pulling the entire drill string. • This is accomplished with an overshot run down the drill pipe on a wire line Advantage Time-saving Disadvantage Smaller core is obtained Sidewall coring www.utm.my Innovative · Entrepreneurial · Global • The coring is done after the drilling • A hollow steel bullet is fired which imbeds itself in formation. It is then retrieved by wire while bullets contain core sample. Steps in core handling and preservation www.utm.my Innovative · Entrepreneurial · Global Mark core barrel’s top and bottom Slightly hammer the barrel to extract the core sample Mark top and bottom on core sample Wrap around each section with wax coating or cellophane paper Mark top and bottom on the 1ft section Place the core sample in wooden boxes before transporting to the lab • Normal routine analysis of the core • Properties to be determined: • Porosity • Permeability • Saturation www.utm.my Innovative · Entrepreneurial · Global Special core analysis (SCAL) Routine core analysis (RCA) Core analysis • Additional analysis added to the normal routine analysis • Including measurements of twophase flow properties, determining relative permeability and capillary pressure • Properties to be determined: • Porosity • Saturation • Permeability • Capillary pressure test • Relative permeability test • Connate water saturation • Wettability • Resistivity • Mineralogical composition • Electric measurement Factors affecting the laboratory saturation • Original fluid content • Properties of reservoir fluid • Rock permeability • Drilling fluid properties • Coring rate • Care of handling www.utm.my Innovative · Entrepreneurial · Global Well Logging www.utm.my Innovative · Entrepreneurial · Global WHAT? • The continuous recording of a geophysical parameter along a borehole produced a geophysical well log. • The value of the measurement is plotted continuously against depth in the well. WHY? • To collect data about wellbores and subsurface formations. • To make critical decisions about drilling, completion and production Well logging www.utm.my Innovative · Entrepreneurial · Global Well logging with a logging tool run down a well on a wireline A wireline well log www.utm.my Innovative · Entrepreneurial · Global • During drilling a liquid mixture containing clays and other natural materials, called Mud is pumped down the drill string forcing the rock cutting up to the surface and decrease the heat from the interaction between the bit and the well wall rocks. • Hydrostatic pressure of the mud column is usually greater than the pore pressure of the formation. • This forces mud filtrate into the permeable formations and a mud cake on the borehole wall. www.utm.my Innovative · Entrepreneurial · Global This makes an establishment of • Flushed zone • Transition zone • Uninvaded zone What logs tell us? www.utm.my Innovative · Entrepreneurial · Global Lithology Porosity Permeability Resistivity Saturation Fluids in the pores of the reservoir rocks Sample of well log www.utm.my Innovative · Entrepreneurial · Global Types of logging www.utm.my Innovative · Entrepreneurial · Global • SP (Spontaneous Potential) Log • Resistivity Log •Caliper Log •Acoustic Log •Temperature Log Mud logging Electric logging Miscellaneous Logging Radioactivity logging •Gamma Ray Log • Neutron Porosity Log Mud Logging www.utm.my Innovative · Entrepreneurial · Global • A detailed record of borehole vs depth by examining the rock cuttings brought to the surface by drilling mud Sample of Mud Log www.utm.my Innovative · Entrepreneurial · Global Electrical logging Spontaneous Potential Log • The SP Log is a record of direct current voltage that develops naturally between a movable electrode in the wellbore and fixed electrode at the surface • Self potential develops due to salinity contrast between mud filtrate and formation water • Reasons for self potential • Liquid Junction Potential • Membrane Potential www.utm.my Innovative · Entrepreneurial · Global Electrical logging Spontaneous Potential Log Interpretation Goals Correlation of formation from well to well Estimation of formation water resistivity (Rw) Useful for Limitations Detecting permeable beds and it thickness Oil based mud or synthetic mud Locating their boundaries and permitting correlation of such beds Same salinity Determining formation water resistivity Mostly used in sandstones Qualitative indication of bed shaliness Air and gas drilling Qualitative indication of permeability Estimation of shale content Detection of permeable beds www.utm.my Innovative · Entrepreneurial · Global Electrical logging Resistivity Log • A sonde sends an electrical signal through the formation and relays it back to a receiver at the surface (induced electricity). • The surface detector will measure the formation’s resistance to the current. • A rock which contains an oil and/or gas saturation will have a higher resistivity than the same rock completely saturated with formation water. www.utm.my Innovative · Entrepreneurial · Global Electrical logging www.utm.my Innovative · Entrepreneurial · Global Resistivity Log Indication of permeability Resistivity of formation water Correlation Porosity Interpretation goals Radioactivity Logging www.utm.my Innovative · Entrepreneurial · Global Gamma Ray Log • Record the natural γ-radioactivity of rocks surrounding the borehole. • The γ-radiation arises from three elements present in the rocks, isotopes of potassium, uranium and thorium. • Useful for defining shale beds because K, U and Th are largely concentrated in association with clay minerals. • It is used to define permeable beds when SP log cannot be employed (eg. When Rmf = Rw). Radioactivity Logging www.utm.my Innovative · Entrepreneurial · Global Gamma Ray Log Interpretation Goals Correlation of formation from well to well Lithology Estimation of shale content Source rock identification Limitations Clean sandstone may also give a high GR response if it contains potassium feldspar, micas, galuconite or uranium-rich water Solution: modified spectral GR Log Radioactivity Logging www.utm.my Innovative · Entrepreneurial · Global Neutron Porosity Log • To obtain a neutron log, a sonde sends atomic particles called neutrons through the formation. • When the neutrons collide with hydrogen, the hydrogen slows them down. • The response of the devise is primarily a function of the hydrogen nuclei concentration. • When the detector records slow neutrons, it means a lot of hydrogen is present – main component of water and hydrocarbon, but not of rocks. • Considered as porosity log because hydrogen is mostly present in pore fluids (water, hydrocarbons) the count rate can be converted into apparent porosity. Miscellaneous Logging www.utm.my Innovative · Entrepreneurial · Global Acoustic Log • Provide continuous record of the time taken in microsecond/foot by sound wave to travel from the transmitter to the receiver and the sonde. • Velocity of sound through a given formation is a function of its lithological and porosity. • Dense, low porosity rocks are characterized by high velocity of sound wave and vise versa for porous and less dense formation. Logging While Drilling www.utm.my Innovative · Entrepreneurial · Global • One of the major drawbacks of wireline information is that it is received several hours to several weeks after the borehole is drilled. • During this time period, the formation can undergo significant alteration, especially in its fluid saturation, effective porosity, and relative permeability. • LWD allow wireline-type information to be available as near as real-time as possible. • Logging While Drilling (LWD) is a technique of conveying well logging tools into the well borehole downhole as part of the bottom hole assembly (BHA). Logging While Drilling (LWD) www.utm.my Innovative · Entrepreneurial · Global Available measurement in LWD technology Gamma Ray Resisitivity Density Neutron Sonic Formation Pressure Formation Fluid Sampler Borehole Caliper Well testing www.utm.my Innovative · Entrepreneurial · Global What? Well testing is a technique which optimizes and develops a reservoir model capable of realistically predicting the dynamic behaviour of zone of interest in terms of production rate and fluid recovery for different operating conditions. Flow Regimes • The different flow regimes are usually classified in terms of rate of change of pressure with respect to time • Steady state flow • Pseudo steady state flow • Unsteady (Transient) state flow Steady state flow www.utm.my Innovative · Entrepreneurial · Global • In the steady state flow pressure does not change with time means pressure at every location in the reservoir remains constant • Example: • Gas cap • Some type of water drives 𝑑𝑑𝑝𝑝 𝑑𝑑𝑡𝑡 =0 Pseudo steady state flow www.utm.my Innovative · Entrepreneurial · Global • When the pressure at different locations in the reservoir is declining linearly as a function of time means with a constant rate production the drop of pressure becomes constant for each unit of time • Pseudo steady state system characterizes a closed system response 𝑑𝑑𝑝𝑝 𝑑𝑑𝑡𝑡 = 𝑐𝑐𝑜𝑜𝑛𝑛𝑠𝑠𝑡𝑡𝑎𝑎𝑛𝑛𝑡𝑡 Transient state flow www.utm.my Innovative · Entrepreneurial · Global • The fluid flowing conditions at which the rate of change of pressure with respect to time at any position in the reservoir is neither zero nor constant • The pressure variation with time is a function of the well geometry and the reservoir properties such as permeability and heterogeneity 𝑑𝑑𝑝𝑝 𝑑𝑑𝑡𝑡 = 𝑓𝑓(𝑥𝑥, 𝑦𝑦, 𝑧𝑧, 𝑡𝑡) www.utm.my Innovative · Entrepreneurial · Global Input Data www.utm.my Innovative · Entrepreneurial · Global Well data Wellbore radius Well geometry Depths Reservoir and fluid parameters Formation thickness, h Porosity Water saturation, Sw Oil viscosity Formation volume factor Compressibilities Information Obtained from Well Testing www.utm.my Innovative · Entrepreneurial · Global Characterize the ability of the fluid to flow through the reservoir and to the well Provide the description of the reservoir in dynamic conditions As the investigated reservoir volume is relatively large, the estimated parameters are average values From pressure curve analysis, it is possible to determine the following properties: • Reservoir Description • Permeability • Reservoir Heterogeneities • Boundaries • Pressures • Well Description • Production Potential • Well Geometry Types of Well Testing (oil) www.utm.my Innovative · Entrepreneurial · Global Drawdown Test Buildup Test Injection Test/ Fall of Test Interference Test and Pulse Testing Drill Stem Testing Repeated Formation Test (RFT) Drawdown Test www.utm.my Innovative · Entrepreneurial · Global • A pressure drawdown test is a simply series of bottom hole pressure measurements made during a period of flow at constant producing rate. • Usually the well is shut-in prior to the flow test for a period of time sufficient to allow the pressure to equalize throughout the formation i.e. to reach static pressure. • It is difficult to maintain a constant flow rate so drawdown pressure data is erratic. Drawdown Test www.utm.my Innovative · Entrepreneurial · Global Drawdown Test www.utm.my Innovative · Entrepreneurial · Global Buildup Test www.utm.my Innovative · Entrepreneurial · Global • Pressure buildup analysis describe the buildup in wellbore pressure with the time after a well has been shut in. • Before build up test the well must have been flowing long enought to reach stabilized rate. • The flow rate is accurately controlled (zero), that’s why buildup tests should be performed. Buildup Test www.utm.my Innovative · Entrepreneurial · Global Buildup Test www.utm.my Innovative · Entrepreneurial · Global Drill Stem Testing www.utm.my Innovative · Entrepreneurial · Global • A drill stem test (DST) is a temporary completion of a wellbore that provides information on whether or not to complete the well. • The zone in question is sealed off from the rest of the wellbore by packers, and the formations' pressure and fluids are measured. Data obtained from a DST include the following: • fluid samples • reservoir pressure (P*) • formation properties, including permeability (k), skin (S), and radius of investigation (ri) • productivity estimates, including flow rate (Q) • hydrodynamic information Analyzing the DST www.utm.my Innovative · Entrepreneurial · Global Perfect chart. Gauge located inside and above the closing tool. (A) Add cushion/run in hole; (B) initial flow period; (C) initial shut-in period; (D) final flow period; (E) final shut-in period; and (F) pulling out of hole. Collar leak. Gauge located inside and above the closing tool. Chart indicates increasing pressure during running in hole and shut-in periods. Fluid loss from drill pipe. Gauge located inside and above the closing tool. Bleeder valve on drill string left open during shut-in periods. Perfect chart. Gauges inside above and outside below the closing tool. Pressure transient analysis done from these gauges. (A) Run in hole, gauge measuring hydrostatic pressure of mud column; (B) initial flow period; (C) initial buildup; (D) final flow period; (E) final buildup; and (F) release packer and pulling out of hole. Perfect chart. Blanked off gauge below the bottom packer on a straddle test. (A) running in hole; (B) initial flow period; (C) initial buildup; (D) final flow period; (E) final buildup; and (F) pulling out of hole. Bottom packer failure. Blanked off gauge below bottom