Drilling Engineering I PDF

Drilling Engineering I Course Contents: Introduction to drilling methods. Rotary drilling operations. Rig components and their functions. Bit type selection and evaluation. Drilling fluids: functions, types, and compositions. Mud properties and calculations. Mud pump ratings and horsepower requirem...

Drilling Engineering I Course Contents: Introduction to drilling methods. Rotary drilling operations. Rig components and their functions. Bit type selection and evaluation. Drilling fluids: functions, types, and compositions. Mud properties and calculations. Mud pump ratings and horsepower requirements. Drilling hazards and their remedies. Pressure relationship in the formation and bore hole. The hydrostatic fluid head including mud and cement slurries. Drilling Operations and Equipment’s: (Drilling: Drilling operations – Location to Rig. Release Well Bore Diagram, Crews – Operator – Drilling, contractor – Third Party Services. Rig Types: Land Types , Marine types. Main offshore fields, Challenges, Effects on environment Components: Overall Drilling Rig, Drilling Sub systems – Power – Hoisting Line – speeds and Loads Power – Loading Components – Drill Pipe, Heavy Weight Drill Pipe (HWDP), Drill String Loads Uni-axial. References 1. Petroleum engineering handbook, Drilling and well completions, C.Gatlin 2. Applied Drilling Engineering – Adam T. Bourgoyne – SPE Textbook Drilling: is physically creating the borehole in the ground that will eventually become an oil or gas well. This work is done by rig contractors and service companies in the oil field business sector. On a well site, there can be as many as 30-40 different service contractors providing expertise to the operator. THE WELL An oil well is any bore drilled through the Earth's subsurface layers and it is designed to find and gain hydrocarbons. The well is being drilled by complex dangerous methods called (drilling process). The well that is designed to produce mainly or only gas may be termed a gas well. Each well has a criterion called well life which is divided into segments are:  -Planning. -Drilling. -Completion. -Production. -Abandonment 1- Well planning Well planning is perhaps the most demanding aspect of drilling engineering. Although well planning methods and practices may vary within the drilling industry, the end result should be a safely drilled, minimum-cost hole that satisfies the reservoir engineer’s requirements for oil and (or) gas production. Every well whether an exploration, appraisal or development well, is drilled according to a pre- determined plan. The plan is a programme of guidelines or steps to be followed as drilling progresses. Drilling: Bit selection (largest bit first) Before the new well is drilled by an operating company a Site Preparation process starts firstly, this includes:  Road and Piling (if required)  Survey drill site  Install Conductor/Drive Pipe When site preparation completed, drilling Rig and auxiliary equipment move in. Complicated methods used to create oil or gas well use heavy duty tools and at the same time very developed. In terms of technological advance , these methods developed during time. The drilling process is very expensive and dangerous. Two drilling methods are used Cable Tool Drilling and Rotary Drilling which is the most common oil well drilling method. 3- Completion: Completion is the process in which the well is enabled to produce oil or gas, contains: a) Cased-hole completion, small holes called perforations are made in the portion of the casing which passed through the production zone, to provide a path for the oil to flow from the surrounding rock into the production tubing. b) Open hole completion, often 'sand screens' or a 'gravel pack' is installed in the last drilled, uncased reservoir section. These maintain structural integrity of the wellbore in the absence of casing, while still allowing flow from the reservoir into the wellbore. 4- Production: The production stage is the most important stage of a well's life, when the oil and gas are produced. By this time, the oil rigs used to drill and complete the well have moved off the wellbore, and the top is usually outfitted with a collection of valves called a Christmas tree or production tree. These valves regulate pressures, control flows, and allow access to the wellbore in case further completion work is needed. From the outlet valve of the production tree, the flow can be connected to a distribution network of pipelines and tanks to supply the product to refineries, natural gas compressor stations, or oil export terminals. 5- Abandonment: A well is said to reach "an economic limit" when its most efficient production rate does not cover the operating expenses. The economic limit for oil and gas wells can be expressed using special formulas. At the economic limit there often is still a significant amount of unrecoverable oil left in the reservoir. It might be tempting to defer physical abandonment for an extended period of time, hoping that the oil price will go up or that new supplemental recovery techniques will be perfected. In these cases, temporary plugs will be placed downhole and locks attached to the wellhead to prevent tampering. For example the first oil well in Iraq at Baba Gurgur field was abandoned and killed in March ,2012 after 85 years of continuous production at a rate of (100000 bbl/day ) which is more than the reserves of many countries. Types of Well:  Wild Cat  Exploration  Evaluation  Production  Injection  Infill  Observation  Disposal Wildcat Well:  No known or little geological information for site selection. Drilling into a geological structure in which no oil or gas has yet been discovered.   A rank wildcat is drilled at least 2 miles away from any known production. If the well does discover a new field, it is called the discovery well for that field. Exploration Well :  Site selection based on seismic data, satellite surveys, etc. No known drilling data in the prospective horizon.  The exploratory well can be drilled to: Determine the presence of hydrocarbons. Provide geological data (cores, logs) for evaluation. Flow test the well to determine its production potential, and obtain fluid samples. Production or development Well  Wells drilled in the known extent of the field are called developmental well. Infill Well Wells drilled between producing wells in an established field to increase the production rate are called infill wells. Injection well: A well through which fluids are injected into an underground stratum to increase reservoir pressure and to displace oil. Disposal well : A well, often a depleted oil or gas well, into which waste fluids can be injected for safe disposal. Disposal wells typically are subject to regulatory requirements to avoid the contamination of freshwater aquifers. Classification (on shore ) According to a wells final depth, it can be classified into: Shallow well: < 2000 m  Conventional well: 2 000 m -3500 m Deep well: 3500 m -5000 m Ultra deep w ell: > 5 000m Cable Tool Drilling A cable tool rig is relatively simple. The hoisting system consists of a tower with four legs called the derrick that was originally wooden and 70 to 85 ft. high. An engine, originally a steam engine, causes a wooden or metal walking beam to pivot up and down on the Sampson post. The bit, a solid, steel rod about 4 ft. long with a chisel point on it, is suspended down the well from the opposite end by a rope or cable. As the walking beam pivots, it causes the rope and bit to rise and fall. The bit pounds the well down by crushing the rock. The rope or cable is wound around a reel called a bull wheel The rope or cable goes up over a single wheel (crown block) at the top of the derrick and then down to a temper screw on the walking beam and down the well to the bit. As the well is pounded deeper, more rope or cable is let out by turning the temper screw on the end of the walking beam. After drilling 3 to 8 ft, the bottom of the well becomes blocked with rock chips. The bit is then raised, and a bailer is lowered into the well on to remove the rock chips and water. After the bailer is raised and emptied, the bit is lowered into the well to pound deeper. Heavy casing is run down the well from wire rope wound around a wheel. The wire rope runs through a multiple sheave crown block at the top of the derrick. The casing (large diameter pipe) is used in the well to keep water from filling the well and to prevent the sides from caving in. Lighter equipment, such as the bailer, is run in the well on a sand line from the sand reel. Cable tool drilling is very slow with 25 ft/day. It does not effectively control subsurface pressures, and blowouts were common during cable tool operations. However, all fields that were discovered during the 1800s were drilled by cable tool rigs. A cable tool rig in New York drilled a well to a depth of 11,145 ft. in 1953.  Rotary Drilling The main five functions of rotary rig are: 1. Hoisting: The function of the hoisting system is to get the necessary equipment in and out of the hole as rapidly as is economically possible. The principal items of equipment that are used in the hole are drillstring, casing, and miscellaneous instruments such as logging and hole deviation instruments. The major components of the hoisting system are: a) Derrick. b) Block and tackle system. c) Drawworks. d) Miscellaneous hoisting equipment such as hooks. elevators, and weight indicator. 2. Rotating: A rotating system consists of three main sub-systems:  Drill Bit  Drill string  Rotating Mechanism 3. Circulating: the main functions of circulating process are  Control subsurface pressure  Remove cuttings from the hole  Cool and lubricate the drill stem and bit 4. Controlling: The aim of this step is to prevent the uncontrolled flow of formation fluids to the wellbore. The flow of formation fluids into the well in the presence of drilling fluid is called a kick. 5. Power System The power generated by the power system is used principally for five main operations: (1)Rotating (Rotary Table) (2)Hosting (Drawworks) (3)Drilling fluid circulation (Mud Pumps) (4)Rig lighting system (5)Hydraulic systems Site Preparation  To drill a well, a surveyor accurately determines the well location and elevation. A map of the site is prepared and registered with the appropriate government agency. A bulldozer can be used to grade an access road to the site. The bulldozer then clears and levels the site.  A large pit, the reserve pit, is dug and lined with plastic next to the drilling rig. It will hold unneeded drilling mud, cuttings, and other materials from the well.  If it is going to be deep well, a rectangular pit (cellar) can be dug and lined with cement. The cellar provides space below the drilling platform for the blowout preventers.  Provisions are made for a water supply at the drilling site by drilling a water well or by laying a water pipeline.  A rig is assembled during rig up. The start of drilling a well is called spudding in.  Introduction Drilling Team Comprises of:  Drilling contractor’s personnel.  Operating company representatives – Petronas , ExxonMobil, Shell, Murphy.  Service companies –Halliburton, Schlumberger, BJ Services.  Supply companies. Function of Drilling Engineer  To prepare drilling programs; modified drilling program cost estimations.  There are various drilling contracts: daily rate, turnkey, footage rate, and incentive.  To work with geologist (on logging program), and other specialists such as mud engineer, service and supply companies. DRILLING RIG A drilling rig is a machine which creates holes (usually called boreholes) in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas wells, or they can be small enough to be moved manually by one person. ROTARY DRILLING RIG SIZES Land drilling rigs can be classified according to the drilling depth into different sizes: 1- Light duty rigs: drill holes from about (3000-5000 ft) deep or (1000-1500 m). 2- Medium duty rigs: drill to depth ranging from (4000-10000 ft) or (1200- 3000 m). 3- Heavy duty rigs: drill holes from about (12000-16000 ft) deep or (3500- 5000 m). 4- Ultra heavy duty rigs: drill holes from about (18000-25000 ft) deep or (5500-7500 m). HOISTING SYSTEM This system suspends, raises and lowers the entire weight of drillstring, casing and the necessary equipment such as logging and hole deviation instruments in the hole. It performs the same function as a crane. The hoisting system components: Derrick and substructure Draw-work Drilling Lines Crown Block Travelling Assembly such as hooks, elevators, and weight indicator Derrick The most visible part of the hoisting equipment is the derrick, the tall tower- like structure that extends vertically from the well hole. If a drill bit needs to be changed, either due to tear or a change in the subsurface rock, the whole string of pipe must be raised to the surface. Whenever the drillstem is suspended by the traveling block and drill line, the entire load rests on the derrick. The standard pyramid derrick is a structure with four supporting legs resting on a square base. The derrick is erected on a substructure which supports the rig floor and rotary table and provides work space for the equipment on the rig floor. The derrick and its substructure support the weight of the drillstem at all times, whenever it is suspended from the crown block or resting in the rotary table.  Derrick SUBSTRUCTUR A substructure is the framework located directly over the hole; it is the foundation of the rig. The bottom of the substructure rests on level ground. The crew places a work platform on top of the substructure called the rig floor. The substructure raises the rig floor to approximately 10 to 40 feet (3 to 12 metres) above the ground. Elevating the rig floor provides room under the rig for special high-pressure valves and a blowout preventer (BOP) stack that the crew connects to the top of the well’s casing. The exact height of a substructure depends on the space needed for this equipment. A cellar also provides more space for the equipment. Rigid Substructure Travelling Block, Crown Block, Drill Line & Hook Use to connect the supporting derrick with the load of drill pipe to be lowered into or withdrawn from the borehole. During drilling operations, this load usually consists of the weight of the drill pipe, drill collars and drill bit. The drill line passes from the drawworks to the top of the derrick. From here is sheaved between the crown block and traveling block to give an eight, ten or twelve-line suspension. It is then clamped to the rig floor by the deadline anchor. Suspended from the travelling block, on standard drilling systems, is the hook which when drilling carries the swivel and Kelly. The Drawworks The drawworks is a mechanism commonly known as a hoist. The main purpose of the drawworks is to lift the drillstring out of and to lower it back into the borehole. The drill line is reeled (spooled) on a drum in the drawworks. When engaged, the drum turns and either reels in the drill line to raise the traveling block, or lets out the drill line to lower it. Because the drillstem is attached to the block, it is raised or lowered. One outstanding feature of the drawworks is the brake system, which enables the driller to easily control a load of thousands of pounds of drillpipe or casing. An integral part of the drawworks is the gear (transmission) system. This gives the driller a wide choice of speeds for hoisting the drillstring. Lifting System components Moving Kelly to Single in Stabbing Mouse hole the Pipe Single Added Ready to Drill Making a mouse hole connection  How a Block and Tackle Works Imagine that you have the arrangement of a 100 pound (45.4 kilogram) weight suspended from a rope, as shown here. In this figure, if you are going to suspend the weight in the air then you have to apply an upward force of 100 pounds to the rope. If the rope is 100 feet (30.5 meters) long and you want to lift the weight up 100 feet, you have to pull in 100 feet of rope to do it. This is simple and obvious. Now imagine that you add a pulley to the mix. The following figure shows the arrangement after adding a second pulley This arrangement actually does change things in an important way. You can see that the weight is now suspended by two pulleys rather than one. That means the weight is split equally between the two pulleys, so each one holds only half the weight, or 50 pounds (22.7 kilograms). That means that if you want to hold the weight suspended in the air, you only have to apply 50 pounds of force (the ceiling exerts the other 50 pounds of force on the other end of the rope). If you want to lift the weight 100 feet higher, then you have to reel in twice as much rope 0- 200 feet of rope must be pulled in. This demonstrates a force-distance tradeoff. The force has been cut in half but the distance the rope must be pulled has doubled. The following diagram adds a third and fourth pulley to the arrangement. In this diagram, the pulley attached to the weight actually consists of two separate pulleys on the same shaft, as shown on the right. This arrangement cuts the force in half and doubles the distance again. To hold the weight in the air you must apply only 25 pounds of force, but to lift the weight 100 feet higher in the air you must now reel in 400 feet of rope. A block and tackle can contain as many pulleys as you like, although at some point the amount of friction in the pulley shafts begins to become a significant source of resistance. Derrick floor plan The total load FD, however, is not evenly distributed over all legs of the derrick.  In a conventional derrick, the drawworks is usually located between two of the legs.  The dead line must be anchored close to one of the remaining two legs.  The side of the derrick opposite to the drawworks is called V–gate. This area must be kept free to allow pipe handling. Therefore, the dead line cannot be anchored between legs A and B.