RU2012777C1 - Method for well construction - Google Patents

Abstract

FIELD: well drilling. SUBSTANCE: method includes drilling of well, forming side working in well walls at the depth of lowering of casing string. Workings are formed for each intermediate casing string with height ensuring force for adhesion of cement stone to each casing string which counteracts the pushing out force. Casing string is run into well. Prior to injection of grout into each intermediate casing string, hydraulic seal in form of viscous fluid with corrosion inhibitors is injected in amount enough to fill hole clearances of these strings above side workings. Then, grout is injected. Producing formation is perforated before running tubing string into well. After lowering of tubing string, hole clearance of this string above producing formation is filled with viscous fluid to form hydraulic seal with density ensuring hydrostatic pressure exceeding formation pressure. In so doing, side workings are additionally formed in top and bottom of producing formation. Besides, when exposing formations liable to hydraulic fracturing and losses of mud, injected to said formations is viscous fluid - hydraulic seal of density less than that of viscous fluid - hydraulic seal injected below these formations. Hole clearance above producing formation is filled with viscous fluid-hydraulic seal featuring density ensuring hydrostatic pressure exceeding formation pressure by 10-5% . Before lowering of tubing string, producing formation may be perforated. Tubing strings may be provided with packer. EFFECT: higher reliability of isolation of hole clearance and provision of recovery of casing string. 5 cl, 1 dwg

Description

 The invention relates to the oil industry, in particular to a method for constructing wells, securing and isolating casing of various types.

 A known method of building wells, including drilling a well, running a casing, pumping cement into the casing and pushing it into the annulus [1].

 The disadvantage of this method is the low reliability of sealing annular space at the contact of the casing with cement stone, as well as in the intervals of unstable and absorbing formations.

 Closest to the proposed method is a method of building wells, including drilling a well, forming side workings in the walls of the well at a depth of the casing, lowering the casing, injecting cement into the casing and pushing it into the interval of the side workings [2].

The known method has the following disadvantages:
- cement in the annulus, throughout the depth from the bottom to the mouth of the casing and production casing, creates a rigid structure, especially in the zones of contact of cement with rocks. A design with hard contacts due to the destruction of the cement ring due to temperature fluctuations, impacts (for example, perforations, during the descent and ascent of tubing, etc.) forms micro- and macrocracks in the thin cement ring through which migration as hydrogen sulfide ions occurs, and hydrocarbon ions on them to the surface, in the annulus, destroying the metal of the pipes and polluting groundwater, groundwater and air. After one or two repairs, about 25-30% of cement is retained in the annulus in height;
- short well life, since it is impossible to replace the spent, corroded or broken production casing, since it is fully cemented;
- at the moment of cement mortar setting, a sharp depression is created on the reservoir, since the cement hangs on the pipe columns, which can lead to annular manifestations, emissions passing into the fountains, with serious consequences;
- the inability to provide control and impact through the annulus in emergency situations, since the annulus is blocked by cement;
- columns of metal pipes, especially in wells at hydrogen sulfide deposits, are destroyed rapidly, especially the production string, which determines the durability of the well. But it cannot be replaced, since it is fully cemented;
- large and unjustified costs of cement;
- with the existing method, the higher the strength characteristics of cement are created and used during pipe fastening and insulation, the stricter the construction of the structure becomes, the equilibrium conditions of the law of flexible construction systems in the contact zone of artificial with natural materials are violated, since the coefficients of linear and volumetric changes in metal, cement and natural mountain vapors are different, contacts are broken during perforation, impacts and temperature fluctuations, therefore, cement cannot qualitatively solve simultaneously tasks of fastening columns and their isolation;
- the inability to use anti-corrosion inhibitors under the condition of flexible contacts to preserve metal columns, since they are completely cemented.

 The present invention eliminates these disadvantages and reduces the cost of well construction.

 Any multi-volume, multi-meter in height and length structures should represent a flexible system, with structures moving in contact with the natural environment, without violating the integrity of the structure when exposed to natural forces (temperature fluctuations, shock, earthquakes, etc.), since violation of these construction conditions will result to premature destruction of the structure.

 For many decades, during the construction of a well, the problem of providing impermeable, flexible contacts of cement with rocks and pipe metal has been solved, since the safety and durability of well construction structures are mainly determined by the quality and durability of these contacts, which would not depend on objects and linear changes in materials. This determines the general flexible equilibrium state of the entire artificial structure (well) with natural rocks as a whole. The second main criterion for a flexible, durable system of a structure should be protected against corrosion and the possibility of replacing spent units and structures. But such a durable construction of the well has not yet been possible to create, since cement was used as a fastening and insulating material, which, creating rigid contacts, performed the pipe fastening task well, but did not provide isolation conditions and flexibility, movable contacts, especially with temperature fluctuations, impacts etc.

 The necessary technical result is achieved by the fact that according to the method of well construction, including well drilling, formation of side workings in the walls of the well at the depth of the casing, lowering the casing, pumping cement into the casing and pushing it into the interval of the side workings, the latter are formed for each from the intermediate casing strings and perform their height, which ensures the adhesion force of the cement stone to each of the casing strings, which counteracts the buoyancy force, and before injection a viscous cement slurry into each of the intermediate casing strings with corrosion inhibitors, a viscous hydraulic fluid is pumped in the annulus of these strings above the side workings, while the production stratum is perforated before the production strings are lowered, and after the production strings, the annular space above the stratum is filled with viscous fluid -gidrozat with a density that provides hydrostatic pressure above the reservoir pressure. In this case, lateral workings are additionally formed in the roof and sole of the productive formation. In addition, when opening formations prone to fracturing and absorption, a viscous hydraulic sealant fluid of lower density is pumped above these layers than the density of a viscous hydraulic sealant fluid below these layers. Also, the annular space above the reservoir is filled with a viscous hydraulic sealant fluid with a density that provides hydrostatic pressure 10-15% higher than the reservoir pressure. In this case, prior to the descent of the production casing, the formation is perforated. In addition, tubing is used as the production string, the latter being equipped with a packer.

 The essence of the invention lies in the fact that the fastening of the casing strings is carried out not over the entire annulus, but only at the wellhead for the next casing and in the bottom zone (casing shoe) using cement stone in a volumetric output in the borehole walls. Before the cement is pumped as an insulating material - a water seal, represented by a viscous fluid of specified parameters depending on the parameters of the reservoir, treated with corrosion inhibitors with cementitious materials. The production string is lowered, for example, on a packer. The column is not cemented.

 A method of constructing a well is shown in the drawing.

 Before the descent of each pipe string, geophysical work is carried out, according to the results of which the intervals of lateral workings are determined. Production is determined based on the forces that push the pipe string out of the well. Lateral concentric workings are carried out by known methods, for example, hydraulic fracturing using a hydraulic monitor, local explosions of directional action, etc.

 After the conductor 1 is lowered, a viscous hydraulic fluid prepared as required is pumped, and then a cement mortar is injected into the output volume, and the displacement is carried out with a normal solution. Cement mortar fills the production, forms a screen 2 in the zone of the shoe of the column (above it - a water seal). Next, the intermediate technical column 3 is drilled. They also make a hole, lower the column, pump a viscous fluid - a water trap 5-6, cement mortar into the mine 7 and push it with a normal solution pump. In this case, clutch 4 (3-4 m) is represented by only one corrosion inhibitor. The rest of the annulus is a stable hydraulic lock of the given parameters. In the roof of the screen (3-4 m above the cement), a left sub (with a large thread) is installed before lowering the technical column (left sub are not indicated).

 In cases of upper weak strata, prone to rupture and absorption, hydraulic locks 5-6 of lower density are pumped higher than the lower ones. All cement screens 2, 7, 17, 19 are kept from moving upward columns. At the mouth of the column is attached to the next column of pipes. After the drilling of the design layer, the ring workings for the screens 17, 19 are developed in the roof and sole, the pipe casing - liner 9 (liner) is lowered, while the sleeve 8 is installed in the intermediate string zone, and in the gap - viscous fluid - a water seal 10, with a density that provides 10-15% excess pressure of the reservoir. Clutch 8 is represented by an 8-10-meter cement ring in the presence of intermediate reservoirs. Blowing, cementing the shank is carried out with a viscous fluid - a water seal of the same composition. After perforation of the formation, the production string is lowered (or tubing, depending on the presence of gas or oil in the formation), but in both cases with the following arrangement: packer 13, above it is the left sub 16, the check valve 14 with remote control. Under the check valve 14, a clutch 15 is installed with a fitting - a compensator that prevents sand from falling into the sump from the reservoir (with sharp pressure drops). A perforated pipe (liner) - 18 is installed below the packer.

 Behind the production casing, a trap is left with the specified parameters, also treated with anti-corrosion inhibitors. At the mouth, all annular spaces are equipped with level sensors, gas analyzers with samplers 20.

 In some cases, perforation of the reservoir is carried out before the production string is launched.

 A composition based on monoethanolamine (up to 0.02%), polyacrylamide, aluminum sulphate, drilling mud, and an anti-corrosion inhibitor can be used as a viscous hydraulic fluid. The viscosity of the composition (conditional) is not less than 100 s.

 In all cases, especially in hydrogen sulfide deposits, the packer, pipe stability is modeled in special chambers with downhole conditions and with monitoring equipment. Data on the model signals the need for a column change. On command, the check valve is activated. In this case, the heavy fluid of the hydraulic seal 14, entering the pipes, presses the formation. If necessary, pump up a heavy solution. After the formation is crushed, the column is hoisted to replace the spent units and structures. One of the features is that the design of the well provides for the replacement of only the upper parts of the casing strings.

 The shank (liner) 9 is lowered as usual on the drill pipe. The shank funnel is equipped with a large left-hand thread.

Claims (5)

 1. WAY OF CONSTRUCTION OF WELLS, including drilling a well, forming side workings in the walls of the well at the depth of the casing, lowering the casing, injecting cement into the casing and pumping it into the side workout interval, characterized in that when constructing deep oil and gas wells with with a multicolumn construction, the latter are formed under each of the intermediate casing strings and are made of their height, which provides the adhesion force of the cement stone to each of the casing strings, counter viscous buoyancy, and before injecting the cement slurry into each of the intermediate casing strings, a viscous hydraulic fluid is injected with corrosion inhibitors in the volume of the annular space of these strings above the side workings, while the productive formation is perforated before the production casing is lowered, and its casing is capped the space above the reservoir is filled with a viscous hydraulic sealant fluid with a density that provides hydrostatic pressure above the reservoir pressure.  2. The method according to p. 1, characterized in that the side workings are additionally formed in the roof and sole of the reservoir.  3. The method according to PP. 1 and 2, characterized in that at the opening of formations prone to fracturing and absorption, a viscous hydraulic sealant fluid of lower density is pumped above these layers than the density of a viscous hydraulic sealant fluid below these layers.  4. The method according to PP. 1 and 2, characterized in that the annular space above the reservoir is filled with a viscous hydraulic sealant fluid with a density that provides hydrostatic pressure 10-15% higher than the reservoir pressure.  5. The method according to p. 1, characterized in that the tubing is used as the production string, the latter being equipped with a packer.

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