Reservoir Rock Mechanics Formation Evaluation PDF

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...

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 packer on a straddle test. When the bottom packer fails, the pressure gauge will read some flow and buildup data but will not replicate gauges run above the bottom packer because of a restricted flow area around the packer elements.