RU2057905C1 - Method of borehole fixing and gear for its implementation - Google Patents

Abstract

FIELD: borehole drilling. SUBSTANCE: this method of borehole fixing involves filling of hole clearance with nonhardening viscous-ductile grouting with required strength of structure which is determined by calculation. After exploitation is terminated casing pipes are removed out of borehole. Gear for implementation of method has two concentric pipes which are radially connected by means of metal bushings. Stoppers made of material readily soluble in acid are screwed into them. EFFECT: reliable separation of seams opened by borehole without decrease of their productivity factor. 2 cl, 3 dwg

Description

 The invention relates to drilling and well development and is intended for the oil and mining industries.

A known method of fixing formations uncovered by a well, filling the annulus with cement mortar [1]
The disadvantage of this method is the gradual deterioration of the structure of cement stone, starting from the moment of injection, hardening and in the process of finding the cement mortar in a static state over time.

 Known methods for fastening wells [2,3,4] in which the process of blocking the channels of the permeable medium of the productive formation occurs as a result of the penetration of the solid parts of the solution into the channels of the formation, as well as the filtrate of the drilling and grouting fluids, followed by their compaction due to the difference between the bottomhole and reservoir pressure.

 The disadvantage of these methods is the reduction of the reservoir productivity coefficient, which occurs during the fastening of the wells as a result of the mismatch of the quality parameters, chemical properties of the solution and technological processes with the geological conditions of well construction.

The closest analogue of the invention is a method of securing wells, including lowering the casing, and filling the annular space with a gel-like grouting mixture [5]
A gel-forming solution prepared from a carboxylate-containing polymer, which is crosslinked by a complex consisting of a chromium component and carboxylate groups in contact with a permeable medium (oil-bearing formation) also does not exclude the occurrence of pressure in the formation at a certain pressure drop.

 In the process of injecting a cement mortar, it is mixed with buffer and drilling fluids. While waiting for cement to harden as a result of pressure reduction, osmotic and capillary phenomena, penetration and filtration of formation fluid through the forming cement stone occurs. As a result of the action of temperatures and different values of the coefficients of expansion of the casing strings and cement stone, the latter experiences a pressure that varies in magnitude and sign. A great influence on the behavior of the stone up to the destruction of its integrity have perforation. The cement mortars used exclude the possibility of correcting poor-quality separation of the formations without perforation of the casing strings and removing the casing strings after completion of the complex of hydrodynamic studies and well operation operations.

A device for fixing wells is known, comprising two concentrically arranged with a gap spaced pipes with packer units at the ends and a drive for opening the packer units [6]
The disadvantage of this device is the technological and constructive complexity of the application, since the device is manufactured of a certain length in the factory without taking into account the peculiarities of the geological conditions of the reservoir of the reservoir (cavities, the presence of aquifers, etc.).

 The objective of the proposed technical solution is the reliable separation of the layers exposed by the well, without reducing their productivity coefficient.

P_пл.max-P

10⁶, мг/см²
где θ_f(t) прочность структуры нетвердеющей вязко-пластичной тампонажной смеси изменяющейся по величине до определенного времени, мг/см²;
Р_пл.max-Р_пл.min приведенные к одной глубине Н пластовые давления двух горизонтов, имеющих разные градиенты давления и залегающие на глубинах Н_х и Н_у, кгс/см²;
h x_x-x_y расстояние между пластами, имеющими аномальные градиенты давления, см;
D диаметр скважины, см;
d наружный диаметр обсадных труб, см;
k коэффициент проницаемости пористой среды, куда возможно поглощение тампонажной смеси;
α- безразмерный коэффициент для глинистых и цементных растворов;
( α= (2,8-4,5) х 10^-5);
D_в диаметр глубины проникновения нетвердеющей вязкопластичной жидкости, см;
Кроме того, технический результат достигается тем, что устройство для селективной изоляции пласта содержит две концентрично с зазором расположенные трубы с пакерующими узлами на концах. Устройство снабжено полыми втулками, соединяющими трубы друг с другом и сообщающими через их полость внутренней трубы с внешним пространством, при этом полые втулки выполнены с пробками из легкорастворимого в кислоте материала, перекрывающими полость втулок.The task is achieved as follows. The method of fastening wells includes filling the annulus with a non-hardening viscoplastic cement mixture, the structural strength of which satisfies the condition:
θ _{f (t)} ≥

P _pl.max -P

10 ⁶ , mg / cm ²
where θ _{f (t} ) is the strength of the structure of a non-hardening visco-plastic grouting mixture varying in value up to a certain time, mg / cm ² ;
P -P _{pl.max pl.min} reduced to the same depth H of the two horizons reservoir pressures, having different gradients and pressure at depths H _x and H _y, kgf / cm ^2;
hx _x -x _y distance between formations having abnormal pressure gradients, cm;
D well diameter, cm;
d the outer diameter of the casing, cm;
k the permeability coefficient of the porous medium, where the absorption of cement mixture is possible;
α- dimensionless coefficient for clay and cement mortars;
(α = (2.8-4.5) x 10 ^-5 );
D _{in the} diameter of the penetration depth of non-hardening viscoplastic fluid, cm;
In addition, the technical result is achieved by the fact that the device for selective isolation of the formation contains two concentrically arranged with a gap located pipes with packer nodes at the ends. The device is equipped with hollow bushings connecting the pipes to each other and communicating through the cavity of the inner pipe with the outer space, while the hollow bushings are made with plugs of readily soluble in acid material that overlap the cavity of the bushings.

 The proposed method of attaching wells and a device for its implementation do not require cementing with hardening grouting mortars (cement), since the annular space is filled with a non-hardening viscoplastic grouting mixture (NVTS) with a design strength of the structure that ensures uncoupling of the layers of the opened well, even if there is a difference in pressure gradients between layers, for example, clay-oil mixtures.

 After treating the well with acid, a plug of readily soluble metal dissolves and a message opens in the annulus of the column with the reservoir. At the same time, the annulus of the column, filled with a non-hardening viscoplastic cement mixture, remains tight with respect to the inner tube space of the column due to the connection of two concentric pipes of the device with metal bushings. This eliminates the flow of grouting mixture into the column while reducing the pressure in the column to the required technological value during the development and operation of the well.

 Figure 1 shows a device for attaching wells; figure 2 the layout of the bottom of the casing when used and the elements of the device in the working position; figure 3 is a schematic diagram of the temporary fastening of wells by simultaneously overlapping two reservoirs using the device: a) the final position after the grouting mixture is pushed into the annulus; b) the situation in the development and research of the first object; c) the situation in the development and research of the second object.

 A device for implementing the method (Fig. 1) consists of a set of sections with plugs screwed into metal bushings 1, packer elements 2 interacting with a wedge 3, a piston 4 is placed between the casing 5 ms by circulation holes 6 and cylinder 7, safety screws 8, saddles 9 of the shutoff valve, ball 10, couplings of casing pipes 11, casing 12, washer-trap 13.

 The complete assembly of the device consists in connecting the upper and lower sections having couplings 11 by means of a pipe 5 and a casing 12. The mating ends of the casing 12 are connected to the upper and lower sections by welding.

 The use of a set of pipes allows you to assemble a device of any estimated length between the packing elements, i.e. overlap any thickness of the reservoir.

 The method of attaching wells includes blocking the reservoir 14 (Fig. 3) using a device 15, centralizers 16, a non-hardening viscoplastic cement mixture 17, a dividing bridge 18.

An example of the implementation of the method: a well with a diameter of 215.9 mm with a deflated column with a diameter of 146 mm is considered. The design well depth is 1550 m, productive formations with a pressure gradient of 1.15 kg / cm ² per 10 m of depth occur in the intervals of 1510-1500 and 1350-1345 m, aquifers with pressure gradients of 0.85 kg / cm ² per 10 m at a depth of 1100 m with a thickness of 15 m. The permeability coefficient of an aquifer lying at a depth of 1100 meters is 0.5 darsi.

 The devices, together with casing pipes, are lowered into the well and installed in the intervals of 1510-1500 m and 1350-1345 m with precise reference to radioactive logging.

 Next, a ball 10 is dropped into the casing string and the circular circulation of the drilling fluid in the well is restored. When the ball 10 is seated on the saddle 9, the pressure is raised, and with its value of 4.5-5 MPa, the safety screws 8 break in the packer units, the pistons 4 with wedges 3, moving in the axial direction, push the packing elements 2 against the walls with conical ends wells, thereby sealing the roof and bottom of the reservoir. With a further increase in pressure to 9 MPa, the studs of the saddle 20 of the maximum pressure are cut, the ball 10 with the saddle 9 falls on the catcher 13 (Fig. 1 arrangement of the bottom of the casing) and the circulation in the borehole is restored through the annular space between the USIP body and the casing .

After that, the calculated volume of 42.2 m ^{3 of} non-hardening viscoplastic cement mixture is injected into the casing 5 (Fig. 1), which, passing through the shoe of the casing, holes in the lower packing element 2 (Entrance in figure 1), the annular space between concentric pipes and holes (Exit in figure 1) in the upper packing element 2, falls into the space between the walls of the well and the casing 5, bypassing the reservoir.

As the column of a non-hardening viscoplastic cement mixture increases, the rubber elements become even more self-sealing, thereby completely protecting the productive formation from contact with the cement mixture. The well plugging process ends with the cork plug being put on the TsKOD saddle, which serves as a stop ring due to the anomalous value of reservoir pressure gradients at various depths, taking into account the depth of penetration of a non-hardening viscoplastic cement mixture into the aquifer, the value of the structure strength of the cement mixture is determined by formula 1 , which is 2357 mg / cm ² excluding the penetration of the mixture into the aquifer. Taking into account the penetration of the mixture into the permeable medium, D _at 30 cm, the strength of the mixture structure will be θ 377 kg / cm ² . After determining the estimated value of the structural strength of the grouting mixture, it is necessary to pay attention to prevent rock wall collapses, the value of θ should be at least 1500 mg / cm ² .

After waiting for the estimated time to set the strength of the cement mixture structure (about 24 hours), the tubing is lowered into the well below the interval of the USIP installation (first object) by 15 m, i.e. to a depth of 1525 m. Hydrochloric acid is pumped with a calculated volume of 1 m ³ to break the tube of a metal readily soluble in acid, screwed into metal bushings, in order to open communication channels between the annulus of the column with the reservoir.

 After completion of development, hydrodynamic research and operation of wells, if necessary, casing is removed from the well. Then the wells are liquidated or canned according to the applicable environmental guidelines for well construction.

Claims (2)

1. A method of fastening wells, including the launching of casing pipes, filling the annulus with a gel-like grouting mixture, characterized in that a non-hardening viscous-plastic grouting mixture is used as the grouting mixture, the structure strength of which must satisfy the condition

where θ _{f (t) is the} structural strength of a non-hardening viscoplastic cement mixture, which varies in value up to a certain time t, mGy / cm ² ,
P _{n L. m a x} - P _{n L. m i n} reduced to the same depth H reservoir pressures of two horizons having different reservoir pressure gradients and occurring at depths H _x and H _y , kgf / cm ² ;
hx _x x _y distance between formations having abnormal pressure gradients, cm;
D well diameter, cm;
d the outer diameter of the casing, cm;
K the permeability coefficient of the porous medium absorbing the grouting mixture, Darcy;
α dimensionless coefficient for clay and cement mortars (α = (2.8-4.5) • 10 ^-5 );
D _{in the} diameter of the penetration depth of a non-hardening viscoplastic fluid, see  2. A device for fastening wells, containing two concentrically arranged with gaps located pipes with packer nodes at the ends and a drive for opening the packer nodes, characterized in that the device is equipped with hollow bushings connecting the pipes to each other and communicating the cavity of the inner pipe with the outer space through their cavity while hollow bushings are made with plugs of readily soluble in acid material overlapping the cavity of the bushings.

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