Oil Well Rig and Directional Drilling Technology: A ...

International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015

Oil Well Rig and Directional Drilling Technology: A Field Investigation Prasenjit Dutta1, Nabarun Biswas2, SujoyChakraborty3, Srijit Biswas4 1,2,3

Assistant Professor,Dept of PE,NIT Agartala. M.Tech Scholars,Dept of PE, NIT Agartala.

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[email protected] [email protected] [email protected] [email protected]

Abstract—when there are some critical stages, only the conventional rotary drilling techniques cannot be used to extract oil from beneath the earth’s surface. The present field study aims at understanding the art and science of drilling oil wells. The prime focus of the work will be on well drilling in the oil and gas industry, meanwhile it is worth to emphasize, that wells can be drilled for a variety of purposes.The technical complexity is so great that no single company is diverse enough to perform all the required work. Consequently, many companies and individuals are involved in drilling a well, including operating companies, drilling contractors, and service and supply companies. So an understanding of the techniques related to the drilling of oil wells using the technological marvels in the present era will be worth for future endeavors.

1.

INTRODUCTION

Knowledge of oil extraction techniques and the functions of the components of an oil well drilling set up are very much essential on the part of a mechanical engineer. The underlying operating principles of the equipment are same as discussed by various author(s) or what were taught to us. The conventional and directional drilling techniques comprise of the same rig set up and operating components, only a few tools set up change is there for directional drilling for obtaining target depth. The primary objective of the work will be an investigation of the major components of rig layout system elements practically part by part and to present a work study meticulously about these components and the techniques of operation. The present field study aims at understanding the art and science of drilling oil wells. The prime focus of the work will be on well drilling in the oil and gas industry, meanwhile it is worth to emphasize, thatwells can be

drilled for a variety of purposes. Not all wells are used to extract oil and gas from the earth. Wells are also drilled to produce fresh water for irrigation and to supply water to cities. Some wells are drilled into deep layers of rock to dispose of hazardous waste. Greenhouse gases, such as carbon dioxide, can be captured and injected into underground layers for permanent disposal. The same well drilling methods can be applied to all these uses. 2.

PLAN OF STUDY

Phase-I 1) Paper research to develop general information, comparison study in between rotary drilling technique and cable tool drilling technique. 2) Technical sessions on the backdrop of crude oil in Assam and its exploration throughout. 3) Theoretical demonstrations in oil well rig layout and the components of conventional drilling methods. 4) Demonstration of types of drilling fluid and its additives. 5) Presentation to conceptualize the basic motive behind directional drilling and its applications. 6) Establish preparatory information to continue in Phase II: a)

Recommendations on what should be studied.

b) General safety precautions to be taken up in the rig zone. c)

A listing of chances of possible accidents in an oil field.

589 © Malla Reddy Engineering College (Autonomous)

International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015 Phase-II 1) Visit to an active oil rig and field inspection on the basic components of the rig layout. a)

Field demonstrations on component parts of the rig.

various

b) Field demonstration on power house and circulatory system of the rig. c)

Identification and nomenclature structural components on a rig.

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2) Technical visit to the rig while directional drilling is in progress. a)

Demonstration on tools and equipment used in directional drilling technique and terminologies of directional drilling.

cannot pass naturally. Without traps, the oil and gas could migrate all the way to the surface and evaporate. Oil is formed from the remains of tiny plants and animals (plankton) that died in ancient seas between 10 million and 600 million years ago. After the organisms died, they sank into the sand and mud at the bottom of the sea. Over the years, the organisms decayed in the sedimentary layers. In these layers, there was little or no oxygen present. So microorganisms broke the remains into carbon-rich compounds that formed organic layers. The organic material mixed with the sediments, forming fine-grained shale, or source rock. As new sedimentary layers were deposited, they exerted intense pressure and heat on the source rock.

b) Observations of the operation. 3) Visit to the rig when production process is tested. The overall sequence of the works to be taken up during the stipulated time period is presented here in a flowchart form as shown. 3.

OIL EXPLORATION

Oil is a fossil fuel that can be found in many countries around the world. Oil and gas are naturally occurring hydrocarbons. Two elements, hydrogen and carbon, make up a hydrocarbon. Because hydrogen and carbon have a strong attraction for each other, they form many compounds. The oil industry processes and refines crude hydrocarbons recovered from the earth to create hydrocarbon products including: natural gas, liquefied petroleum gas (LPG, or hydro, gas), gasoline, kerosene, diesel fuel, and a vast array of synthetic materials such as nylon and plastics. Crude oil and natural gas occur in tiny openings of buried layers of rock. Occasionally, the crude hydrocarbons ooze to the surface in the form of a ship, or spring. More often, rock layers trap the hydrocarbons thousands of feet (meters) below the surface.

Figure 1 Close-up of reservoir rock (oil is in black) (Photo courtesy Institute of Petroleum)

The heat and pressure distilled the organic material into crude oil and natural gas. The oil flowed from the source rock and accumulated in thicker, more porous limestone or sandstone, called reservoir rock as shown in figure 1. These movements of the Earth include: 1) Folding - Horizontal movements press inward and move the rock layers upward into a fold or anticline. 2) Faulting - The layers of rock crack, and one side shifts upward or downward. 3) Pinching out - A layer of impermeable rock is squeezed upward into the reservoir rock.

3.1 The Formation: Oil and Gas (Hydrocarbons) are substances found within the earth’s crust, formed from decomposed plant and animal matter, with pressure and temperature over the time. Oil and gas are found in natural traps within the earth. These traps consist of domes or faults. Impermeable rock above the trap prevents the oil and gas from migrating up to surface. An “impermeable” rock is one through which fluid

Figure 2 Entrapment of oil and gas amidst rock layers (Photo courtesy Institute of Petroleum)


International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015 4.

OIL WELL DRILLING Basically two type of well is drilled: 1) Exploratory wells- to find out new fields. 2) Development wells-well drilled to get the production from old fields. 4.1 The Drilling Operation: The crew sets up the rig and starts the drilling operations. First, from the starter hole, they drill a surface hole down to a pre-set depth, which is somewhere above where they think the oil trap is located. There are five basic steps to drilling the surface hole: 1) Place the drill bit, collar and drill pipe in the hole. 2) Attach the kelly and turntable and begin drilling. 3) As drilling progresses, circulate mud through the pipe and out of the bit to float the rock cuttings out of the hole. 4) Add new sections (joints) of drill pipes as the hole gets deeper. 5) Remove (trip out) the drill pipe, collar and bit when the pre-set depth (anywhere from a few hundred to a couple-thousand feet) is reached. . Drilling continues in stages: They drill, then run and cement new casings, then drill again. When the rock cuttings from the mud reveal the oil sand from the reservoir rock, they may have reached the final depth. At this point, they remove the drilling apparatus from the hole and perform several tests to confirm this finding:  Well logging - lowering electrical and gas sensors into the hole to take measurements of the rock formations there  Drill-stem testing - lowering a device into the hole to measure the pressures, which will reveal whether the reservoir rock has been reached  Core samples - taking samples of rock to look for characteristics of reservoir rock Once the well is completed, they must start the flow of oil into the well. For limestone reservoir rock, acid is pumped down the well and out the perforations. The acid dissolves channels in the limestone that lead oil into the well. For sandstone reservoir rock, a specially blended fluid containing proponents (sand, walnut shells, aluminum pellets) is pumped down the well and out the perforations. The pressure from this fluid makes small fractures in the sandstone that allow oil to flow into the well, while the proponents hold these fractures open. Once the oil is flowing, the oil rig is removed from the site and production equipment is set up to extract the oil from the well.Figure3.1 shows the layout of a drilling rig. 4.2 Rig Components: As the layout shows a rig comprises of many different parts. A derrick, a substructure, hoisting equipment, engines for power, Motors, PCR house, Steel tanks, mud pumps, solids control equipment, Compressor and many

other types of equipment. Rig equipment can be classified broadly under: 1) Hoisting & Rotating system 2) Power system 3) Circulating system 4) Well control system 4.3 Conventional Drilling Activities 4.3.1 The Hole Making Process: It is the process of creating a path in subsoil, includes breaking rock in consolidated sediments and stirring in unconsolidated sediments. Most of the hole making process is through mechanical methods, but other means of high frequency vibration & Hydraulic pressure is also being used. Mechanical means of hole making are classified as follows: 1) Cable tool drilling – Heavy string of drilling tools frequently lifted & dropped into hole breaking the consolidate rock into fragments. These fragments are formed into slurry and lifted out of hole by bails. 2) Auger Drilling – Done with a helical screw driven into ground with rotation, the drilled earth is lifted by the blade of helical screw. Repeated same till the required depth is used. Used for site investigation, environmental / Geotechnical drilling & sampling, bore holes for construction process

Figure 3.Rotary drilling set up


International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015

Figure 4 A layout of a rig


International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015 Rotary Drilling – Rotating sharp drill bits used to dig into earth’s crust. Drilled cuttings are picked up & cleared out of the bore hole by drilling fluid. 4.3.2

Rotary Drilling:

In rotary drilling, the disintegration of the rock occurs as a result of a concurrent action on the bit of a load and a torque it shears it. Cuttings from the hole are carried to the surface by drilling mud which is circulated continuously through the drill string. The mud is pumped into the drill pipe at the surface, out through the bit, and up the annular space between the drill pipe and the walls of the hole. 4.3.3

1

Caliper log

Bore hole size deviation

2

Spontaneous

Sand shale boundaries

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Gamma ray log

Sand shale boundaries / well to well correlations/depth correlations

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Resistivity log

Measures resistivity / support tool along with other tool

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Sonic log

Porosity

acoustic

Drilling Phase:

During the wellbore making phases, there are several operations performed at the same time to have better control over the process. These are discussed here. Logging Operation:Well logging is a technique to record geophysical properties of rock as a function of depth. It is accomplished by moving a down hole logging probe and recording its sensor output at the surface through an electrical cable. The borehole logging probe or the well logging tool relates to a particular physical property of the rock and mud system. The well logging system consists of(a) Down hole-logging tool, (b) Surface computer system and (c) Wire line cable for transmitting down hole signal to surface system.

Coring Operation: Particularly during the exploration phase of a field, coring presents an important means to calibrate the petro-physical model and gain additional information about the reservoir not obtainable by logs. Usually the decision of when and where to core will be made in conjunction with the geologist and operations department, taking into account the costs and data requirements. Cementing Operation: Oil well cementing is the process of mixing and displacing a slurry down the casing and up the annulus, behind the casing, where is allowed to “set”, thus bonding the casing to the formation. Some additional functions of cementing include: 1) Protecting producing formations.

Majority of logs are recorded while pulling the tool upward in the borehole. The logs are recorded both in the open hole as well as in the cased hole, though with different objectives. There is a large variety of logging tools meant for different types of measurements. Generally these tools are named according to what parameter they measure or to the physical process involved during their operation e.g. the tool which measures resistivity of the formation is resistivity log. Table-I: Different Logging instruments S.N.

NAME LOG

OF

MMEASURED PARAMETER

2) Providing support for the casing. 3) Protecting the casing from corrosion. 4) Sealing off troublesome zones. 5) Protecting the borehole in the event of problems. The main ingredient in most cements is “Portland” cement, a mixture of limestone and clay. This name comes from the solid mixture resembling the rocks quarried on the Isle of Portland, off the coast of England. There are two types of cementing process:


International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015 1) Primary cementing 2) Secondary cementing. The cementation that take place soon after the lowering of casing is called the primary cementation and any cementation job after primary cementation is known as secondary cementation. 4.3.4 Drill Bit: The drill bit is the tool that attached at end of the drill string that actually cuts up the rock; comes in many shapes and made of materials that are specialized for various drilling tasks and rock formations. Type of drill bits: 1) Drag / Wing /Blade / Fish tail bits: Having tungsten carbide cutting surfaces for drilling unconsolidated formations. Cutting action is shearing action on the formation. 2) Tricone roller bits (TCR bits): Having rollers individually rotate against their respective bearing axis. Cutting action is crushing or chipping. These bits may be of Milled tooth or Tungsten carbide insert bits. 3) PDC bits: Polycrystalline diamond compact inserts attached to steel or matrix body blades. 4) Diamond bits: Industrial diamonds imparted on them for drilling. Besides these some special types of bit are available for some special operation. The performance of the drill bit is dependent on many factors such as selection of proper bit, operating parameters and hydraulics. Figure 5 shows different bit types.

Figure 5 Drill bits (source ONGC, mechanical engineering handbook)

5.

INTRODUCTION TO DIRECTIONAL DRILLING There are many reasons for drilling a directional wells, including: 1) Side-tracking existing wells (because of hole problems or fish or reaching new targets). 2) Restricted surface locations. 3) To reach multiple targets. 4) To reduce number of offshore platforms. 5) Horizontal Drilling. 6) To reach thin reservoirs (using horizontal or multilateral drilling).

7) Salt dome drilling (direct the well away from the salt dome to avoid casing collapse problems). 8) Geological requirements, reservoir beneath natural obstruction (mountains) Or severe topographical features. 9) Reservoir beneath population centers. 10) Relief well to plug a blowout. So basically directional drilling can be defined as… Directional drilling is the art and science involving the intentional deflection of a wellbore in a specific direction in order to reach a predetermined objective below the surface of the earth or it can be defined also as…“Science of directing a wellbore along a predetermined trajectory to intersect a subsurface target”. 5.1 Directional Drilling Terminologies: 1) Measured depth (MD): Actual depth of the well measured through drill string. 2) Course length (CL): Measured length between two survey stations. 3) Drift angle or inclination angle (degrees): Deviation from vertical. 4) True vertical depth (TVD): True vertical depth as calculated from directional survey. 5) Departure or course deviation: Horizontal distance the well has achieved. 6) Drift direction (Azimuth): The well direction from north measured in degrees. 7) Build up angle: The build-up angle is given in degrees per unit of length. 8) Kick-Off point (KOP): The well depth at which deflection of the hole is initiated. 9) Monel drill collar: A non-magnetic drill collar in which compass is positioned for measuring hole inclination and direction. 10) Closure or horizontal drift: Horizontal distance and direction to any specified point in the hole. 11) Lead angle: The practice of anticipating the normal direction and angle at which the bit will drill. 12) Bottom hole orientation (BHO): Method used to orient directional tool in the desired direction. 13) Declination: Angular difference between magnetic north and true north direction. 5.2 Types Of Directional Well Profiles: There are three factors which are to be considered before selecting a profile. 1) The distance between the surface location & reservoir location. 2) Type of the formation down below. 3) The production policy. Three types of profile are universally adopted – 1) Type-I or Build & hold profile 2) Type-II or ‘S’ type profile 3) Type-III or ‘J’ type profile 5.1 Type-I / Build and Hold Profile:


International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015 Construction wise, this profile has three sections a) Top vertical portion. b) Build up portion. c) Hold portion. This builds and hold profile is used in those areas where a requirement of horizontal drift predominates. It has thus found its maximum use in cluster drilling, both on offshore & onshore areas. In fact, the horizontal drilling has been possible with this profile only. This profile is suitable for penetrating high dipping formations, because the horizontal portion cuts the beds orthogonally and the crookedness of inclined bed is effectively counter-acted. The rate of production is reduced if the pay horizon is cut at an angle more than 36 degree. Also, the secondary recovery methods like SRP’s are unsuitable for this type of profile. Figure 4.6 shows this profile.

Figure 6 Type-I profile 5.2 Type-II / S-Profile: It consists of five partsa) Top vertical portion b) Build portion c) Hold portion d) Drop portion. e) Bottom vertical portion This profile is very suitable for those situations where the pay horizon is to be cut vertically. Incidentally,

this is the best profile from production point of view, but practically these two curved portions (build & drop) give the well a crooked type of construction ,and is the beset with problems like severe torque & drag. “S” type of profile is adopted for those situations where the horizontal drift requirement is much less vis-àvis the TVD of the well. This profile is also useful where the gumbo formations or steeply dipping beds are to be drilled vertically. Figure 7 shows this profile. Figure 7 Type-II/ S-profile 5.3 Type-III/ J-Profile: Third profile is J type that is long vertical & deep kick off. Here in the well is deviated from a deeper depth & the angle is build up according to the required horizontal drift. Obviously, the profile is use where the horizontal drift requirement is much less & hence it finds much use in the industry.Figure4.8 shows a J-type directional profile. 5.4 Geometry Of A Directional Well: The following parameters define directional well. 1) Inclination: It is the angle between vertical and tangent to the well path at any point. 2) Azimuth: It is the angle measured in horizontal plane between the direction of north and the point on the well path. thus, a point with an azimuth of 50 means that the direction of the point is at 50 from the north. In practice, two northern direction are recognized, geographic and magnetic north. Geographic north refers to the north-pole, while magnetic north specifies the northern direction of the earth’s magnetic field. 3) True Vertical Depth It is the true vertical depth from the surface to the target. It is the vertical distance measured from a reference point to the survey point. TVD is usually referenced to the rotary table, but may also be referenced to mean sea level, 4) Horizontal Displacement It is the horizontal distance from the target zone from the platform reference point. The horizontal displacement and azimuth of the target at any point on the well path can be used to determine the northing and easting coordinates of the point in question. 5) Dog-Leg It is defined as the angular change between two points on the well path, and can result from changes in inclination, direction or both. The dog-leg over specified depth interval is termed as ‘dog-leg severity’. 6) Kick-Off Point It is the point at which the well is deflected from vertical. 5.5 Drilling Fluids: A drilling fluid is any fluid which is circulated through a well in order to remove cuttings from a wellbore. A drilling fluid must fulfill many functions in order for a well to be drilled successfully, safely, and economically. The most important functions are: 1) Remove drilled cuttings from under the bit


International Conference On Emerging Trends in Science Technology Engineering and Management 09th & 10th, October 2015 2) Carry those cuttings out of the hole. 3) Suspend cuttings in the fluid when circulation is stopped. 4) Release cuttings when processed by surface equipment. 5) Allow cuttings to settle out at the surface. 6) Provide enough hydrostatic pressure to balance formation pore pressures. 7) Prevent the bore hole from collapsing or caving in. 8) Protect producing formations from damage which could impair production. 9) Clean, cool, and lubricate the drill bit. General composition of drilling fluids 1) The Base Liquid: a) Water - fresh or saline b) Oil - diesel or crude c) Mineral Oil or other synthetic fluids 2) Dispersed Solids: a) Colloidal particles, which are suspended particles of various sizes 3) Dissolved Solids a) Usually salts, and their effects on colloids most is important Special Drilling fluids: 1) Lime Base Muds. 2) Emulsion Muds - Oil in Water. 3) Gypsum Base Muds. 4) Silicate Muds etc… 5.6 Drilling Monitoring: The overall Well progress compared with reference to the well program. The monitoring is generally carried through: 1) Real Time Monitoring through SCADA systems 2) Managerial supervising 3) Communication channels like Radio Channels, Phones, Mobiles etc Monitoring of the following are done at base level: 1) Geological aspects being encountered 2) Depths Drilled 3) Directional control as per plan 4) Casing lowered depths 5) Drilling rates / bit effectiveness 6) Drilling fluid effectiveness 7) Time progress 8) Safe & Standard procedures 5.7 Cost Components: The Cost Components of Drilling of a well 1) Well material component: Based on the geological objective, well program to be firmed up. The estimation of well material is worked out from the same. 2) Operational cost of drilling a well: Based on the cost of utilising rig, equipment, manpower etc. for drilling operations and dependant of the time for operations. 3) Preparatory cost component:

Land acquisition and Civil works cost of a well CONCLUSION In an E&P Company about 40-50% of the annual budget is being utilised in Drilling of wells. Any contribution towards performance improvement and cost reduction in drilling operations (critical activity in finding/producing oil) leads to enhanced returns. Drilling has developed into a specialized and technologically advanced business. The size of the equipment is enormous. The technical challenges to overcome as wells become deeper and are drilled in increasingly hostile environmentsare equally enormous. The technology of the most advanced drilling rig is computer-controlled and can be monitored from any office in the world. A smaller number of wells, located even at a great distance from sensitive and protected areas, imply a significant reduction in the infrastructures necessary to develop and keeps a field in production, such as drilling sites, service roads, parking areas, and means of transport. All of this implies less pressure on the area with great advantages for the environment. During the entire project investigation the primary objectives were partially fulfilled. The directional drilling technique is a very vast field to be studied, during this work basic knowledge in the field of directional drilling is acquired. The operating companies have some limitations due to which all the operation and techniques could not be learnt during the stipulated time frame. However, conventional drilling rig system and the drilling methodologies were very elaborately demonstrated with practical field visits. There is a lot of scope in the design principles of each and every part to be studied. Keeping in view, the rapid growth in the exploration of hydrocarbon worldwide and the global energy basket remains dominated by oil & gas which is constitute almost 59% of total primary energy consumption and its availability in Assam, one should have the knowledge of exploration and production technology of the aforesaid mineral. REFERENCE 1) 2)

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Ken Fraser. Managing Drilling Operations. Elseviser Science Publishing Co., Inc., 1991. Edward L Glaeser and Matthew G Resseger. The complementarity between cities and skills*. Journal of Regional Science, 50(1):221–244, 2010. Halliburton. Drilling, 2015. URL http://www.halliburton.com/enUS/ps/sperry/ drilling/default.page?node-id=h8cyv98x. Ryan Kellogg. Learning by drilling: Interfirm learning and relationship persistence in the texas oilpatch. The Quarterly Journal of Economics, page qjr039, 2011. PR Rampersad, G Hareland, P Boonyapaluk, et al. Drilling optimization using drilling data and available technology. In SPE Latin America/Caribbean Petroleum Engineering Conference. Society of Petroleum Engineers, 1994 James A Sorensen and John R Terneus. Evaluation of key factors affecting successful oil production in the bakken formation, north dakota. Technology status assessment. Energy and Environmental Research Center, Grand Forks,
