SU977695A1 - Method for drilling wells under complicated conditions - Google Patents

Description

(54) WELL DRILLING METHOD IN COMPLICATED CONDITIONS

The invention relates to the drilling of a well, in particular to the regulation of bottomhole pressure in the system. well-plates and can be used in drilling oil and gas wells, as well as in drilling wells for water and solid minerals.

There is a known method of drilling a well under complicated conditions in the presence of overpressure, which consists in that the back pressure on the formation, i.e. The bottomhole pressure is regulated by varying the density of the drilling fluid tl.} However, when implementing this method, a necessary condition is to accurately determine such parameters of the formation as the formation pressure. fracture pressure and permeability, which is a complex scientific and technical challenge, since it is necessary to predict these parameters.

The density of the drilling fluid must be constantly maintained within very tight limits due to the value of reservoir pressure in the AHFP zone (upper limit), as well as the value of hydraulic fracturing and intermediate intermediate column shoe and the expected height of the gas bundle in case of an emergency gas release (lower limit). The fulfillment of this condition is a very difficult task, since it is associated with relaxation (stabilization) and stabilization with the help of physicochemical treatment of a large volume (up to 200 m) of circulating drilling mud. At the same time, the choice of treatment formulation must be carried out promptly and accurately. The maximum efficiency of adjusting the density of the drilling fluid corresponds to the time of the complete circulation cycle, which is usually 2-3 hours. The indicated time is not enough to prevent the beginning of oil and gas production or absorption, i.e. regulation of the density of the drilling fluid can not be carried out quickly, which ultimately can lead to oil and gas production, absorption, emission or fountain.

The method of using two solutions with different densities, used to increase the speed of density control, also does not perturb this problem. In the process of drilling formations with overpressure at the drilling site, it is necessary to constantly have a supply of the upgraded solution in the amount of one to two times the volume of the wellbore, and the reserve solution must be periodically mixed, controlled and maintained at the required density. The considered method does not allow opening the horizon with abnormally high pressure without interrupting the intermediate casing of the overlying permeable formations with a lower gradient of reservoir pressure or a low fracture gradient. This necessitates the descent and cementing of several casing strings with alternation of several layers with different anominalities of the reservoir pressure in the well section, as well as layers with different fracture pressure gradients. Ultimately, taking into account the noted deficiencies, the main one being the impossibility of one- and rational density control, this method does not provide a good warning of the occurrence of oil and gas production, gas-oil emissions and fountains, as well as the absorption of drilling mud in the course of well drilling in complex geological fields. conditions Also known is a method of drilling a well under complicated conditions, including regulating the back pressure throughout the wellbore by changing the structural and mechanical properties of the drilling fluid by changing the intensity of the physicomechanical effect on the latter during the drilling process 2. The known method allows adjust the viscosity of the drilling fluid only if there are drill pipes in the wellbore, i.e. for cases when the drill string is lifted from the well (for changing the bit, lowering the next casing string to repair the drilling equipment and other tools, this method does not prevent the occurrence of gas and oil drilling and drilling fluid spraying. Also, the known method is based when special liquids are used as drilling mud, the viscosity of which varies due to the action of the electric field. However, these liquids are very sensitive to the influence of impurities. this fluid as a drilling fluid, its composition and, consequently, its properties constantly vary depending on the content of cuttings in it, formation waters, soluble or dispersed oil and gas impurities. This reduces the reliability of the method and the reliability of preventing oil and gas of drilling fluid absorption and absorption due to possible failures in the power supply system. The purpose of the invention is to improve the reliability of preventing oil and gas penetration and absorption of drilling mud. This goal is achieved by the fact that according to the method of drilling a well under complicated conditions, including the regulation of back pressure throughout the wellbore by changing the indicators of the structural and mechanical properties of the drilling fluid, carried out by changing the intensity of the physical-mechanical effect on the latter during the drilling process, as a drill of the solution, USE extremely, structurally, extremely plastic drilling pass, that, and physicomechanical impact carry out longitudinal vibration drilled coarse with an amplitude of fluctuations within 0.05-2.0 mm and with a frequency within 20-1000 Hz and / or hydro-pulse oscillations in the mud column with an amplitude of 0.1-, 15: kg / cm and s frequency in the range of 20-1000 Hz. . In addition, the maximum dynamic shear stress of the drill: Pastes are chosen in the range of 500-10000 mg / sq. Figures 1 and 2 show a schematic diagram of the implementation of the method, respectively, during tripping and during drilling. The essence of the method lies in the fact that the control of the back pressure on the formations throughout the wellbore is carried out by changing the indicators of the structural and mechanical properties of the drilling fluid, in particular by changing the magnitude of the limiting dynamic shear stress. An extremely structured, high-particle dispersion system with high cohesive strength of particles in a coagulation contact, for example, a highly concentrated sodium bentonite paste prepared on a water basis and treated with stabilizing agents, is used as a drilling fluid. structured limiting-plastic drill paste is a dispersed system with a coagulation structure, for which the flow curve can be constructed only in

the conditions of the vibratory background (the thix treatment process is equal to not less than 100 units, the plasticity according to Volarovich is not less than 100 units)

For example, the following composition can be used as a highly structured, ultimate plastic drilling paste:%: Asian Bentonite 15 Flotation barite 30 Igetan (reagent stabilizer) 0.1 CMC-500 (reagent stabilizer). 0.5 Water Rest The Burova paste of this composition has the following parameters of statistical conditions: density of 1 50 g / cm; viscosity conditions for PV-5 - does not flow, water loss is 1-3 cm, slept / 600 mg / cm, effective in viscosity 50

Thus, the main adjustable parameter is the ultimate shear stress of the drilling fluid. ra.

The adjustment of the structural and mechanical properties of the drilling fluid is carried out by varying the intensity of the vibration impact on it, both mechanically (by vibrating the drill string), and the hydraulic impulses transmitted to the drilling fluid from the mud pump. If necessary, both types of vibration on the drilling mud are combined. In all cases, at the time of stopping the circulation of the drilling fluid in the well, vibration is stopped, and the latter almost instantly assumes the original State, which is characterized by the maximum value of the ultimate shear stress (as well as viscosity, adhesion forces). The maximum ultimate shear stress depends on the composition of the highly structured drill spit ;;; This value is selected so that it, together with the weight of the solution column of a given density, counteracts the pressure of the reservoir with AHWP (taking into account the specified factor of safety) in a static state. Before starting the drilling pumps, the vibration effect is resumed, starting at a predetermined maximum intensity to reduce the starting pressure. After the circulation of the drilling fluid in the well is established, the vibration effect on it is reduced to a predetermined intrinsic value, which is established (for a given constant productivity of the mud pumps and the predetermined rotational speed of the drill pipes). limiting voltage value -

shear of the solution, which provides a predetermined hydrodynamic pressure in the annulus, which, together with the weight of the solution column, exerts a predetermined back pressure on the formation with a maximum pressure gradient (taking into account the specified safety factor).

In order to reduce the likelihood. the absorption of drilling mud by layers that are prone to hydraulic fracturing or absorption and lying above the reservoir with abnormally high air flow during circulation circulates the intensity of vibration affecting the fluid over the wellbore, namely

Intensify the vibration vibration effect on the solution in the bedding interval, where absorption is possible, thereby reducing the hydrodynamic pressure on these layers, and decrease the vibration intensity in the bedding interval with the air-borne pressure bearing layer and its formation. tires, increasing due to this hydrodynamic pressure on; . formations. The probability of the occurrence of significant absorption is small, since the extremely structured, extremely plastic brown paste, which penetrates into the near-stem zone of the absorbing horizon, leaves the area of vibration and takes its initial solid state; impaired absorption development.

The drilling method is as follows.

In the section opened by borehole 1, there is a production horizon 2 with abnormal pressure, an impermeable formation-tire 3 of the production level, a permeable formation 4 with normal plastic pressure and an impermeable formation 5. The upper part of the section is blocked by an intermediate casing b. The drill string layout includes a chisel 7, drill pipe 8 (UBT) and drill pipe 9. To adjust the ultimate shear stress of the drilling fluid by vibrating it throughout the wellbore, a hydraulic lift 10 with a hydraulic pulse is used as the descent gear. an oil pump 11. In addition, a drilling pump of hydro-impulse action 12 is used. The frequency and pitch of the hydraulic pulses of the oil and mud pumps are controlled by means of bypass valves. Therefore, the hydraulic lift, due to the operation of the pulse oil pump, transmits to the drill string longitudinal oscillations, both in the process of its lowering and raising, and when the latter is at rest. A pulsed mud pump generates longitudinal and transverse vibrations of the mud column in the drill pipe and in the annulus when pumping the drilling fluid. Thus, it is possible to carry out a controlled vibration impact on the drilling tool throughout the wellbore during a given time: during the trip-up process, due to vibrations of the drill string; in the process of drilling, working out or flushing, the well - due to joint vibro-, oscillations of the drill string and the mud column, or only due to the latter factor.

The differentiation of the intensity of vibration impact on the drilling fluid through the wellbore is carried out by varying the values of wave resistance in different parts of the drill string. This is achieved due to the fact that the UBT 8 and the 9 kc drill pipes are made of pipes with different stiffness and modulus of elasticity.

Example. The lower part of the section of the gas field of the Vukharo-Khiva gas-oil-bearing region is represented by a gas-bearing high-permeable reservoir 2 with a capacity of 200 m, lying in the range of 2800-3000 m and having a formation pressure gradient P 0.20 kg / cm m; impenetrable reservoir-3 with a capacity of 500 m, lying in the range of 23002800 m; the plate fracture gradient is not known; permeable nepro-. the reservoir 4 capacity, lying in the range of 2200-2300 m and. having a formation pressure gradient of P 0.12 kg / cm m; impermeable layer 5, in the roof of which. the intermediate casing column b was lowered, cemented to the mouth.

The diameter of the intermediate casing 219 mm. Drilling of the borehole 1 in the complicated zone is carried out with a bit 7 with a diameter of 190 mm

using standard drill pipes 8 (drill collars) with a diameter of 146 mm, length 100 m and drill pipes 9 with a diameter of 114 mm. In order to vibrate the drilling fluid in the borehole, a hydraulic lift 10 is used, equipped with a hydraulic pulse oil pump 11, as well as a drilling pump 12 hydroimpulse action. In ((the upper part of the cut is drilled

using normal drilling mud. No income is 30–40 m to the top of formation 2, a string of drill pipes and CNTs are lowered into the well, arranged in such a way that its lower part, which is opposite to the interval of formation of reservoir 3 (and in Dschneyshy and opposite formation 2), has the maximum resist

and the rest of the part is the minimum characteristic impedance. After that, the normal drilling fluid is replaced by a well-structured, extremely plastic drilling paste, by pumping it through the drill pipe to maximize the vibration of the drill pipe and hydraulic pulses so as to minimize the maximum shear stress of the drilling fluid and speed up the process of pumping it into the well. The maximum shear stress of the drilling fluid in the initial state is 2000 kg / s. Based on this, taking into account the known relationship, we determine the pressure that a given drilling fluid, related to the top of formation 2, can prevent. The value of this pressure is about 295 kg / cm for annulus and about 240 kg / cm for pipe space. Similar results are also obtained when drilling a well by a known method. With this in mind, the minimum allowable density of the drilling fluid is in the static state of 1.14 g / cm - or about 1.65 g / cm with a safety factor adopted equal to 1.5 m.

Taking into account the assumed mud density of 1.65 g / cm, the hydrostatic pressure of the solution column at the top of formation 2 is 476 kg / cm, then. as reservoir pressure is 560 kg / cm. Hence, the minimum hydrodynamic pressure in the annulus during drilling is 84 kg / cm. Taking into account a safety factor of 1.2, the required hydrodynamic pressure is about 100 kg / cm.

Drilling begins with a minimum productivity of the drilling pump with its maximum hydroimpulsive effect on the drilling paste. At the same time starting pressure on the pump is minimal. If necessary, in order to reduce the starting pressure, vibration is applied to the drilling solution of the drill pipe, for which, before the start of circulation, the hydraulic pulse oil pump 11 of the hydraulic lift 10 is connected, on which the drill pipes are suspended. The oil pump works through a hydro-pulse by-pass valve, and the hydraulic lift rod remains in a predetermined position. After the start of stopped circulation of the drilling fluid, if necessary, increase the productivity of the mud pump so that

hydrodynamic pressure in the annulus was about 100 kg / cm. At the same time, the rotation of the drill string is started and the well is deepened along the lower part of the formation 3. During the drilling process, the level of the solution in the pump receiving tank is monitored. When a decrease in level is detected, which is a sign of solution suction, the hydraulic pump oil pump 11 of the hydraulic lift 10 is lowered to decrease the hydrodynamic pressure on the absorbent formation 4 by lowering the maximum shear stress of the mud in the upper wellbore under vibration of the drill string. The intensity of vibration of the drill pipe string on the drilling fluid is controlled by changing the intensity of the hydraulic lift oil pump of the hydraulic ram until the signs of absorption are eliminated, i.e. when the main part of the required hydrodynamic Pressure will be created in the lower part of the wellbore in the interval of the layers 2 and 3, and a smaller part in the upper interval. At the same time, the performance of the pulsed drilling pump 12 is adjusted to provide the necessary hydrodynamic pressure in the annulus, taking into account the changed maximum shear stress of the drilling fluid in the upper part of the barrel. Thus, before opening the productive formation 2 in the process of first drilling and using extremely structured extremely plastic drilling paste, the necessary technological parameters of the further drilling process are selected: the performance of the drilling pump and the intensity of vibroinfluence (see the table) for the drilling fluid from the condition of preventing gas emissions from productive formation and absorption in the upper part of the section. After that, the lower part of the formation 3 is broken and the gas-bearing formation 2 is opened. a space of at least 100 kg / cm. In this case, in the event of gas generation, which may be due to an incorrect determination of reservoir pressure or a decrease in the limiting stress of the mud shift,

adjust in the direction of increasing the productivity of the drilling pump (at the same time, the vibration effect of the drill pipes on the drilling fluid is reduced or stopped). In case of occurrence of absorption, the intensity of vibration effects of drill pipes on the drilling fluid is adjusted upwards. In both cases, the corrections regulating the pro-.

10, the injection into the well-reservoir system is almost instantaneous. This allows you to reliably prevent oil and gas penetration and absorption during the drilling process. In addition, when

5, the reservoir properties of the productive formation are maximally preserved. In the static state, absorption is excluded, since the reservoir pressure exceeds the weight of the thrust column. In the process of drilling it is possible for the drilling mud to penetrate only into a limited part of the near-wellbore zone of the formation, since it, immediately after

5 takes on a solid state.

Before starting the lifting operations, the drilling pump is stopped, as a result of which the drilling fluid almost instantly takes up the initial solid state in the well.

0 To reduce the piston effect in the well bore, pulsed operation of the hydraulic ram is activated, by vibrating the drill at the end of the ramp-up

5 pipes with a minimum amplitude and a maximum frequency (see table). Due to this, in the immediate vicinity of the drill pipe walls, the drilling mud becomes maximum.

0, the fluidity, which corresponds to the minimum shear stress, retains in its main mass the shear stress,: close to the maximum. In the process

5 launching a drill string a column of drilling mud in the pipe and annulus; it retains its structural and mechanical properties to the maximum extent, evenly due to this, the part of the reservoir pressure of the gas bearing layer, uncompensated by the weight of the pole. On the other hand, high-frequency, low-amplitude vibration of boring

5 pipes ensures the normal emptying or filling of pipes, respectively, during their ascent or descent, thus preventing the ejection effect in the well. .

0

Thus, by varying the intensity of the vibrations, the ultimate shear stress of the drilling fluid is controlled during operations such as the dredging of the mud.

gin (as well as flushing, processing) and tripping of drill pipes (as well as capacity). In all other cases, when the drilling fluid in the well is at rest, its maximum ultimate stress rdvig is almost instantly restored.

The main values of the controlled parameters during the execution of various technological operations are given in the table, J

In the example shown, the possibility of thermal injection is shown when the Aichia of an uncoupled reservoir with ADFD and an absorbent reservoir is drilled using a bleed solution whose density is lower than the equivalent anomalous pressure gradient. The proposed method does not require precise determination of the values of reservoir pressure to the pressure of hydraulic fracturing of the opened formations. If a highly structural drilling paste is used with a density exactly matching the equivalent pressure gradient of the formation with an abnormal pressure drop, then the reliability of the method in the pipe, after warning of possible complications, is further increased.

Compared to the known, the proposed method of drilling under complicated conditions provides reliable prevention of such complications as oil and gas penetration, fountains and absorption of drilling mud due to the almost instantaneous control of the back pressure on the formation. Reliability of prevention of complications 100%.

The ability to automate the control of the back pressure to the reservoir is provided by using the principle of controlling the shear stress of an extremely structured, extremely plastic drilling paste by physicomechanical methods.

The use of the method allows to simplify the well design, eliminates the need to accurately determine the reservoir pressure and hydraulic fracturing of the reservoir that is opened, eliminates the need to maintain a given mud density within very limited limits, and also ensures maximum integrity of the reservoir properties of the reservoir.

Claims (2)

Claim 1. The method of drilling a well in complicated conditions, including the regulation of back pressure throughout. the borehole by changing the structural and mechanical properties of the drilling fluid, carried out by changing the intensity of the physical and mechanical effects on the latter during drilling, characterized in that, in order to increase the reliability of preventing oil and gas occurrences and mud losses, a highly structured, extremely structured drilling fluid is used plastic drilling paste, and physicomechanical action is carried out by longitudinal vibration of drill pipes with an amplitude of within 0.05-2.0 mm and with a frequency in the range of 20-1000 Hz and / or hydroimpulse oscillations in the column of a drilling fluid with an amplitude in the range of 0.1-15 kg / cm ² · and s frequency within 20-1000 Hz. 2. The method according to claim 1, distinguishing torn with the fact that the ultimate dynamic shear stress of the drilling fluid is selected in the range of 50010000 mg / cm ² ;