RU2273722C2 - Method for water inflow isolation in non-cased horizontal part of production well bore - Google Patents

Abstract

FIELD: oil and gas industry, particularly methods or devices for cementing, for plugging holes, crevices, or the like.

SUBSTANCE: method involves removing pumping equipment from borehole; lowering tubing string in well; injecting hardening water-proofing solution in well through tubing string; forming water-tight layer in front of water-developing formation intervals. The water-proofing solution is cement mix modified with polyvinylacetate reagent taken in amount of 0.25-0.5% by cement weight. The water-proofing solution volume provides filling of hole annuity in non-cased horizontal well bore part through flow string lowered to horizontal well bore part bottom. Then the water-proofing solution is held in well for 2-3 hours and flushed out from the hole annuity by direct or reverse circulation after cement hardening initiation.

EFFECT: reduced time and material consumption.

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Description

The invention relates to the field of oil and gas industry and will find application in the isolation of water inflows in horizontal or inclined sections of the shafts of production wells.

A known method of completing a production well (see RF Patent No. 2068943, 6 E 21 B 33/13, BI No. 31, 1996), according to which non-productive interlayers of a horizontal section of a wellbore of a producing well are isolated with profile pipes, in which isolation of water inflows is also provided .

The known method for implementation requires sophisticated equipment, repeated tripping, most importantly, in the horizontal section of the wellbore it is difficult to achieve a snug fit of the profile pipe to its walls after straightening it by creating it inside its high pressure with subsequent expansion, since the wellbore in the horizontal section has not strictly cylindrical.

There is also a method of isolating water inflows in horizontal or inclined shafts of producing wells (see RF Patent No. 2206711, 7 E 21 B 33/13, BI No. 17, 2003), which provides for filling the production interval of the well with 10-15% hydrochloric acid or mix it with hydrofluoric in technological endurance in the bath mode, forcing acid into the formation, injecting a gelling 0.1-0.6% aqueous solution of polyacrylamide with hardener chromium potassium alum and an acid solution, repeating the injection of a gelling solution of polyacrylamide and a solution of acid lots as they move along the interval of water inflow, holding technological excerpts for gel formation and flushing the well with hydrocarbon fluid.

In this case, the injection of the gel-forming solution and the acid solution into the bottom-hole zone starts from the middle of the water inflow interval, and when re-injecting along the water inflow interval, the concentration of the gel-forming polyacrylamide solution is gradually increased, and when the process is held in the bath mode, the pressure is lower than the absorption pressure.

The disadvantage of this method is the duration of the waterproofing work associated with additional tripping operations to determine the water-developing areas using hydraulic logging, breaking its middle. In addition, the method is not technological, requires the consumption of a large amount of insulating material and acid.

There is also a method of isolating water-producing strata (see RF Patent No. 2152507, 7 E 21 B 33/13, 33/19 BI No. 19, 2000), which includes extracting pumping equipment from the well, lowering the tubing string. into the well, pumping through them an insulating solution with fastening properties and forcing it into an insulated formation under excessive pressure. At the same time, as a grouting mortar, plasticized cement mortar is used with SEPACOL CE-5381 reagent or waste water treatment plants.

The disadvantages of this method include the following.

The method, as well as the above-described analogues, is RF Patent No. 2068943, 6 E 21 V 33/13, BI No. 31, 1996 and RF Patent No. 2206711, 7 E 21 V 33/13, BI No. 17, 2003, require for their implementation of large material and labor costs associated with the installation of a cement bridge with its subsequent drilling after waiting for the hardening of cement (OZZ), as well as time.

A known method of isolating water inflows in horizontal or inclined trunks of producing wells (see RF Patent No. 2101484, E 21 B 43/27, publ. 10.01.98), including removing pumping equipment from the well, lowering the tubing string (tubing) ) into the well and pumping through them a waterproofing solution with hardening properties.

The known method in technical essence is closer to the proposed one and can be adopted as a prototype.

Its disadvantage is the complexity of the technology of waterproofing works associated with the repeated injection of large volume acid and waterproofing solution, as well as the expense of large material resources and time.

The objective of the present invention is to provide a reduction in material resources, as well as time.

The problem is solved by the described method, including the extraction of pumping equipment from the well, the descent of the tubing string into the well and pumping through them a waterproofing solution with hardening properties.

What is new is that opposite the intervals of water-producing strata, an impermeable crust is formed, while a cement mortar modified with a polyvinyl acetate reagent in an amount of 0.25-0.5% by weight to the mass of cement, with a volume providing filling of the annular space of open-hole, is used as a waterproofing solution. horizontal section through the tubing string, lowered to the bottom of the horizontal section of the wellbore, and holding for 2-3 hours, followed by washing it out of the annulus straight or reverse circulation after the start of cement setting.

The presented drawings explain the essence of the invention, in which Fig. 1 shows a well with an uncased horizontally directed wellbore with a tubing string lowered up to the bottom after injecting an insulating solution with fixing properties and pushing it into the annulus. In Fig. 2, it is the same as in Fig. 1, after washing out the insulating solution from the annular space of the tubing from the horizontal section of the open hole borehole, where it is seen that a waterproof screen of modified cement stone has formed opposite to the intervals of water-developing interlayers.

The method is carried out in the following sequence.

By agreement with the geological and technical services of the oil and gas production department, the length of the uncased horizontal section of the barrel 1 of the production well 2, which is to be waterproofed, is determined. Then, pumping equipment is removed from the well and the tubing string 3 is lowered into it until the bottom of its horizontal section (see figure 1). After the preparatory work is completed, consisting in arranging the cementing equipment on a horizontal platform, assembling the injection and water supply lines, collecting water into the measuring tanks CA-320 M and pressure testing the injection line, they begin to prepare a water-insulating solution with hardening (fixing) properties using cement-mixing unit. As such a solution, you can use a cement solution modified with polyvinyl acetate - PVA reagent, in which Moviol - German production is preferably used as the latter. It is bred in cement mixing water in an amount of 0.25-0.5% by weight to the mass of cement. When dissolving in water PVA reagent, domestic or foreign production, especially when mixing cement, foaming of the processed liquids occurs. Therefore, to prevent foaming in water in both cases, it is necessary to add an antifoam (antifoam), for example, Penta 465 in an amount of 10% by volume of the mass of PVA reagent.

For complete dissolution of the PVA reagent of domestic production, the process takes 1-1.5 hours, and foreign - 15-20 minutes. After complete dissolution of the reagents, the liquid for mixing the cement is ready.

After preparation of the modified cement mortar 4 (ICR) and preliminary washing of the well with buffer fluid, it is pumped through the tubing string using cementing units of the CA-320 M type into the well in the amount necessary to fill the annulus of the uncased horizontal section of the wellbore (see Fig. 1 ) After forcing it into the annulus, the well is kept for 2-3 hours. At the same time, a dense and thin impenetrable cement peel is created on the walls of the permeable sections of the wellbore, the formation time of which is no more than 3.5 minutes.

When the cement begins to set, the ICR is washed out of the annulus by creating a direct or reverse circulation of the fluid that does not pollute the reservoir.

Bench tests established that upon contact of the ICR with the rock of the reservoir, a thin and dense impermeable crust forms, which after exposure for 2-3 hours is easily washed off with liquid, and the crust 5 created from the same ICR and aged for the same time, on the contrary intervals water-producing strata 6 reliably grasps with the rock, forming a thin and dense impermeable crust, not washed out when creating a fluid circulation.

This circumstance allowed the authors to use the ICR to create an impenetrable protective screen opposite the water-developing layers in the proposed method for protecting it with a patent.

The impermeable protective crust 5 of the ICR before and after solidification prevents fluid exchange between the well and the formation, and vice versa, between the formation and the well. The formation of a strong impenetrable crust on the well walls is explained by the fact that the PVA reagent molecules, having a Christmas-tree-like shape, fit tightly into the filter channels of the cement crust and clog them.

After flushing the well, the pumping equipment is lowered there and put into operation.

The advantage of the proposed method in comparison with the known ones is that for its implementation it is not necessary to determine the intervals of water-producing interlayers, therefore, it is not necessary to call a geophysical lot for this purpose, since during the implementation of the method the injected waterproofing solution with hardening properties itself detects permeable areas and reliably isolates them creating an impervious screen. The method is technological, does not require the development of special equipment and reduces the time and materials required for waterproofing works.

Claims (1)

A method of isolating the influx of water in an uncased horizontal section of the wellbore of a producing well, including removing pumping equipment from the well, lowering the tubing string into the well, injecting a water-proofing solution with hardening properties through them, characterized in that they form an impermeable layer opposite the water-developing formation intervals the crust, for which a cement mortar modified with a polyvinyl acetate reagent in an amount of 0.25-0.5% by weight of cement is used as a waterproofing solution , with the volume providing filling of the annular space of the uncased horizontal section through the tubing string, lowered to the bottom of the horizontal section of the wellbore, and holding for 2-3 hours, followed by its washing out of the annular space by direct or reverse circulation after the start of cement setting.

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