Tendinţe în realizarea sondelor pentru

exploatarea gazelor de şist

Breakthrough in Drilling of Shale Gas Exploitation Wells

Prof. Dr. Ing. Mihai Gheorghitoiu, PETROLEUM – GAS UNIVERSITY of PLOIESTI

Drnd. Ing. Constantin Constantinescu, TACROM DRILLING SRL, PLOIESTI

-2014-

The features of the deposits where shale gas is confined,

require, for their exploitation, horizontal wells of considerable length. The possibility of drilling long horizontal wells, on average of 2000 m, and also extended reach wells (ERW) with lengths of about 10000 m led to a change in strategy in terms of exploiting a deposit. Production platforms (Pads) are built for which facilities such as roads, water sources, power plants, drilling fluids production and treatment equipment, cuttings and solids processing systems, waste water filtration and treatment plants etc. are provided. Approach roads avoid creating heavy traffic through towns. From these platforms all wells are drilled for reservoir extraction.

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Platforme de foraj - Pads

Part of a drilling platform

Sondele recomandate a se fora de pe aceste platforme

• sonde orizontale • sonde cu raza extinsă de acţiune (ERW) Acest tip de sonde ridică probleme dificile operatorilor şi

anume: - schimbarea traiectului sondei de la vertical la orizontal; - păstrarea traiectului în porţiunea orizontală, de obicei

foarte lungă; - evacuarea detritusului din porţiunea orizontală; - manevrarea garniturii şi realizarea apăsării pe sapă în

porţiunea orizontală, astfel încît să se evite pierderea stabilităţii garniturii şi blocarea mişcării.

Profilul sondelor programul orientativ de construcţie

Profilul sondelor orizontale Este alcătuit dintr-un interval vertical continuat cu un

interval curbiliniu crescător până la orizontală şi un interval rectiliniu orizontal de lungime mare. Programul de construcţie constă din una sau două coloane verticale, ultima tubată cu şiul într-un strat impermeabil, la circa 200-500 m deasupra stratului productiv. Rezervăm această rază de curbură de circa 200-500 m, deoarece intervalul orizontal fiind lung, necesită foraj în mod rotire, iar garnitura trebuie să reziste la solicitări ciclice de lungă durată. Ultimele intervale vor fi echipate conform particularităţilor stratului productiv.

Profilul sondelor ERW Este alcătuit dintr-un interval vertical continuat cu un

interval curbiliniu crescător până la circa 600, cu o deplasare mare (2000-4000 m), urmat de un interval curbiliniu crescător până la orizontală şi un interval orizontal de lungime mare. Programul de construcţie constă din trei-patru coloane, care să închidă primele intervale, urmând ca porţiunea orizontală să fie echipată conform condiţiilor întâlnite în stratul productiv.

Drilling rigs • These rigs are operating performance. They can drills

many wells from a single location, can skid independently in any direction, accommodate existing wells and allow for complementary operations such as logging, casing, completion, production and workover.

• The rigs are granted with automated pipe-handling systems and iron rough-necks, eliminating the need for manual tongs. The wells activity is under computer controls placed in climate-controlled driller`s cabins to minimising human error. AC powered and computer-assisted controls ensures optimization of drilling parameters such as rate of penetration, trip times, directional drilling, casing running, bit work.

Desen al unui sistem Top Drive

Operaţiile care pot fi executate cu sistemele Top Drive

- forajul vertical şi dirijat al găurilor de sondă multiple şi deviate pentru ţiţei şi gaze pe mare sau pe uscat;

- săparea sondelor prin rotirea burlanelor “casing-drilling technique”; - forajul puţurilor pentru apă; - compunerea şi descompunerea paşilor şi a garniturii de prăjini; - carotarea pe lungimea unui pas, diferite operaţii de instrumentaţie; - foraje înclinate, orizontale şi subtraversări (cu instalaţii de foraj înclinat); - frezarea şi spălarea dopurilor de nisip şi ciment din coloane; - corectarea la interior a burlanelor, frezarea dopurilor din fontă; - lărgirea şi corectarea găurii în mişcare ascendentă cu menţinerea circulaţiei; - conectarea cu garnitura de prăjini în oricare punct al cursei pe axa sondei în

cazul unor manifestări (eruptive) ale sondei; - închiderea circulaţiei fluidului de foraj în orice moment.

External and internal Casing Drive System

Drilling string

The drill string has been a necessary piece of equipment in sinking oil wells but also a sufficient one in that it has raised no disturbing problems for drilling operation. Since the last decade of the twentieth century, due to more daring programs concerning drilling depth, hostile environment, directional -particularly horizontal -drilling, the term ‘sufficient’ has gained profoundness only by the increasingly important technical achievements of the constructors, achievements that have turned it into a component more durable and versatile in the face of new challenges. By challenges we mean wells exceeding 12 000 m in depth or 15 000 m in length, wells with a horizontal displacement of more than 12000 m, many of them at above 1800C temperatures, or in CO2 or H2S environment.

Technical achievements in terms of drill string components

• - friction welding, to secure the joints to the pipe body, which largely solved the problem of concentrated loads and of drill string failure;

• - the increased length of the tool joint internal upset and the plastic lining, which solved the problem of seal loss and of failure;

• - heat-treating high-strength steel for components or for the entire drill pipe, with respect to increased corrosion resistance and mechanical strength (Yield strength S-135 for 9 300 daN/cm2 , V-150 for 10 500 daN/cm2 , U-170 for 11 700 daN/cm2 );

• - double shouldered connections, enabling the transmission of a torque exceeding the classic NC by 40% (over 80 000 N-m), a perfect metal-to-metal seal and a significant decrease in pressure drops due to a smaller OD and a larger ID;

Same structure/same strength

Double shouldered connection

• - non-standard joints, which change the type of thread and reduce the ID / OD ratio so as to reduce the circulation pressure, to increase the effective section of axial loading absorption and the transmission of torques, etc.;

• - increased wall thickness up to 100% in order to increase the tensile strength to over 100,000 daN ;

• - the use of lighter materials such as titanium, aluminium, composite materials, in order to reduce torsional and axial stresses caused by friction in ER Wells.

ER Wells drill pipe

Taking into account the above, as well as the specificity of the horizontal and ER wells, we believe that a key component of the drilling strings used in such wells is, as we mentioned before, the compressive service drill pipes, used in the curved sections (particularly in areas in which the inclination increases), but also in rectilinear sections following the curved ones. This use of the compressive service pipes is required by their design.

The compressive service (CS) pipes were designed to solve the problems related to drilling horizontal wells with an average curve radius (about 100 m). Sinking these wells involves using drill pipes both in steering operations (the drilling string does not rotate, but is subject to high bending and compressive loads) and in rotation (when it is subjected to high, alternate bending and compressive loads).

Compressive Service drill pipe

Drilling ER and horizontal wells

There are currently several modern guiding

technologies which may address the problems posed by drilling this type of wells, and here we refer Navigant drilling technology, AutomationTechnology for Directional Drilling, Rotary Steering System, Reelwell Drilling Method, all of which employing MWD, eventual downhole motors.

Navigant drilling technology

Navigant drilling technology employs a downhole motor whose connection to the bearing section is made through a double tilt sub, which provides a certain angle between the motor axis and the bit axis. Two stabilizers are installed on the motor, namely at the upper end of the motor section and the upper end of the bearing housing. Together with the bit it constitutes the three non-collinear points describing the curve created in the steering operating mode

Three non-collinear points describing well axis

Steering – Rotary mode

A MWD system is incorporated in the bottomhole assembly in order to check whether the designed trajectory is maintained. For a change of direction drilling is performed in the steering mode, when the string does not rotate, but merely slides along the well axis and the motor drives the bit causing the direction to change. In order to maintain the direction drilling is performed in the rotary mode (the string is rotating, driving the motor that rotates the bit).

Automation Technology for Directional Drilling During directional drilling, the drill string is driven by axial

sliding in order to put weight on the bit. The pushing force must exceed the axial friction, which can become very high in the horizontal section. The revolving movement of the drill string could decrease the axial friction, but this is not allowed in this drilling method. Instead, a left-to-right twisting movement (rocking action) is used, which allows for the slight pushing of the drill string towards the bottom. The shift from string drilling to directional drilling is made by initiating an automated left-to-right rocking action, of a certain intensity that should applying sufficient weight on bit. The weight on bit is controlled by the amplitude of the applied rocking action, which action is propagated onto the drill string towards the bit on a length proportional to the rocking movement amplitude. The bit is also steered by the left-to-right cyclic twist. However, the rocking action must not cause a twist on the whole length of the drill string, but only as much as necessary to induce a certain weight on bit.

Rotary Steerable System

This is a steering method which, in order to provide an angle between the bit axis and the BHA axis, employs an articulated device driven by eccentric oscillatory hubs. These are pushed into the well wall with a frequency equal to the bit speed, thus forcing the bit to operate along a certain generatrix. When the inclination needs to be changed the oscillatory hubsare driven, and through the articulated device, they push the bit into the well wall toward the desired direction. The BHA has the shape of a very elongated truncated cone, with the larger base towards the bit, thus ensuring that the direction is maintained when the drilling is not directional.

Drilling is carried out with the drill string in rotationat all times, which has several advantages in terms of cuttings removal, of axial handling of the drill string, of preventing sticking and of the wellbore evenness.

Rotary steering BHA

Reelwell Drilling Method • This is a revolutionary method that is used to drill ER wells or wells

with very long horizontal sections. It differs from the previous ones both in the drill string type and in the fluid circulation in the well.

• The string drill is made of two coaxial tubes that facilitate the drilling fluid circulation towards the bit through the annular space between the two tubes, and the return cuttings-carrying fluid through the inner tube. The fluid goes into the drill string from the flow control unit through the top-drive and the top drive adapter facilitating the passage from the top-drive into the annulus of the drill string and from the inner tube of the drill string into the flow control unit

• The circulation is directed from the surface through the flow control unit which is equipped with pumps, valves, fittings, flow meters, pressure gauges, all connected to a control panel. The two coaxial tubes are electrically insulated one from the other, constituting together an electric conductor that supplies the steering and MWD/LWDdevices placed in the bottom hole assembly

Schematic of Reelwell Drilling Technology

. Thus a continuous and highly accurate transmission of the data is provided for a perfect trajectory control. In the annular space between the drill string and the wellbore a drilling fluid is placed whose density and type are determined according to the pressure in the formation pores, and this fluid is not circulated. It provides the pressure control in the horizontal section and the wellbore stability. The complex flow control unit enables modifying the fluid volume and annular level both in vertical and deviated sections; it may even isolate, through the piston system, the fluid in these sections from the fluid in the horizontal interval for a more accurate control of the pressure on formation. The last casing before the horizontal section is run in an interval with a high inclination, 60 - 70 degrees. A special piston system is placed inside it enabling the easy handling of the drill string in the horizontal section that can reach lengths of more than 20 000 m.

Drilling with lightweight fluids

It is a known fact that some special gas can have special properties in certain pressure and temperature conditions. Such a gas is carbon dioxide (CD). In certain pressure and temperature conditions beyond the critical point (7400kPa, 320C), and thus in a supercritical condition, the liquid/gas phase equilibrium separation film fades, and the mixture represents a supercritical phase with a density similar to that of liquids, and a viscosity and diffusivity comparable to that of gas. Thus, supercritical carbon dioxide (SC-CO2) can be easily brought in the drilling string with the currently used drilling technique. In this state it can drive the downhole motor system like any other liquid fluid, and at the exit from the bit nozzles, in a much less pressurised environment of the annular space, it will behave like a gas, exerting a very low pressure on the borehole

Aspects of the coexistence of the carbon dioxide phases around critical conditions

Slide Number 1Platforme de foraj - PadsPart of a drilling platformSondele recomandate a se fora de pe aceste platformeProfilul sondelor �programul orientativ de construcţie�Profilul sondelor orizontaleProfilul sondelor ERWDrilling rigsDesen al unui sistem Top Drive �Operaţiile care pot fi executate cu sistemele Top Drive External and internal Casing Drive SystemDrilling string �Technical achievements in terms of drill string componentsSame structure/same strengthDouble shouldered connectionSlide Number 16ER Wells drill pipeSlide Number 18Compressive Service drill pipe Drilling ER and horizontal wellsNavigant drilling technologyThree non-collinear points describing well axisSteering – Rotary modeAutomation Technology for Directional DrillingRotary Steerable SystemRotary steering BHA Reelwell Drilling MethodSchematic of Reelwell Drilling TechnologySlide Number 29Drilling with lightweight fluidsAspects of the coexistence of the carbon dioxide phases around critical conditions �