RU2283421C1 - Method for water influx or water lost-circulation zone isolation in well - Google Patents

Abstract

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

SUBSTANCE: method involves drilling-in productive reservoir; drilling oil bed section and swabbing well to determine water inflow in well; providing pressure drawdown to move reservoir fluids through wells previously drilled in productive reservoir out of fissured reservoir part and through wells drilled in fissured reservoir part; injecting cement mix through well under pressure of not more than above pressure drawdown, which provides fluid movement through wells drilled out of fissured reservoir part. The cement mix contains oil and plugging Portland cement having density of 1570-1600 kg/m³, wherein the cement is taken in amount of 1.9-2.1 tons per 1 m³ of oil. The cement mix is forced with degassed oil up to full cement mix displacement from well. Cement mix density is gradually increased during injection operation.

EFFECT: increased efficiency of fissured productive reservoir part plugging.

2 cl, 1 ex

Description

The invention relates to the oil industry and can be used to isolate water inflows or absorption zones in the well.

Closest to the proposed invention in technical essence is a method of isolating water-producing strata, which includes drilling a water-developing stratum by drilling, flushing a well, pumping the estimated volume of grout, pushing it into the annulus and removing excess grout. The opening of the water-producing layer is carried out simultaneously with the expansion of the wellbore, and plasticized cement mortar is used as the grouting mortar. For the period of waiting for the hardening of cement in the well create backpressure on the insulated reservoir (RF Patent No. 2152507, publ. 2000.07.10. - prototype).

The known method does not provide reliable isolation of water inflows or absorption zones in a highly fractured formation, characterized by a pronounced fluid flow through the cracks.

The proposed method solves the problem of isolating the fractured part of the reservoir.

The problem is solved in that in a method for isolating water inflows or absorption zones in a well, including opening a productive formation by drilling, forcing cement slurry into the annulus and waiting for the cement to solidify under pressure in the well, according to the invention, after drilling a section of the reservoir, wells are examined for inflow by swabbing, establishing a depression of the movement of formation fluids in wells that opened the formation without falling into the fractured part, and in wells that opened the formation in the fractured part, injection of Res well cement slurry are at a pressure less than the magnitude of depression of promotion of formation fluids in wells, which revealed no formation of cracks in the contact portion, wherein as the cement slurry used oil cement slurry at a ratio of 1 m ³ oil 1.9-2.1 ton grouting Portland cement with a density of 1570-1600 kg / m ³ , and the sale of oil-cement mortar is performed by degassed oil until the oil-cement mortar is completely displaced from the wellbore.

During the injection process, the density of the oil-cement mortar is gradually increased.

The features of the invention are:

1. drilling drilling of the reservoir;

2. the pushing of cement into the annular space;

3. waiting for the hardening of cement under pressure in the well;

4. after drilling a section of the deposit, conducting a well study for inflow by swabbing;

5. establishing a depression of the propagation of formation fluids in wells that opened the formation without falling into the fractured portion, and in wells that opened the reservoir in the fractured portion;

6. injection of cement slurry through the well at a pressure not exceeding the depression of the progress of formation fluids through the wells that opened the formation without falling into the fractured portion;

7. the use of a cement mortar of oil-cement mortar with a ratio of 1 m ³ oil 1.9-2.1 tons of cement Portland cement with a density of 1570-1600 kg / m ³ ;

8. pushing the oil-cement solution with degassed oil until the oil-cement solution is completely displaced from the wellbore;

9. during the injection process, a gradual increase in the density of oil-cement mortar.

Signs 1-3 are common with the prototype, signs 4-9 are the salient features of the invention.

SUMMARY OF THE INVENTION

Currently, there are cases of rapid flooding of oil producing wells with open bottom in the fractured zones of carbonate reservoirs due to the breakthrough of bottom water. Traditional approaches to solving the issue of isolating bottom water in this case are not acceptable, since the formation has two permeabilities, as it were: fractured and collector proper. The proposed method solves the problem of isolating the fractured part of the reservoir with maximum preservation of the properties of the reservoir. The problem is solved as follows.

When drilling wells, it was noticed that during insulating operations by pumping cement mortar, fractured zones that intensely absorb flushing fluid are isolated. Moreover, after isolation from the same intervals, intense oil manifestations were obtained. The paradox was that the physical properties (hydrophobicity) of oily deposits after cement pouring remained unchanged. Therefore, cement penetrates into fractured formations at a pressure lower than in carbonate reservoirs.

To create the proposed technology, wells are studied for inflow by swabbing and the depression of the formation fluid advance is established for the wells that have opened the formation without falling into the fractured part, and for the wells that have opened the reservoir in the fractured part. The difference in depression reaches two orders of magnitude. Thus, the depression of the propagation of formation fluids through the wells that opened the formation without falling into the fractured part is 3.5–4.0 MPa, and by the wells that opened the reservoir in the fractured part, it is about 0.05 MPa. In order to prevent the cement slurry from entering the reservoir, it is necessary to maintain the injection pressure below the depression of the movement of formation fluids through the wells that opened the formation without falling into the fractured part, i.e. below 3.5-4.0 MPa. After the cement mortar is poured, technological exposure is carried out under the pressure of the squeeze. In this case, an oil-cement mortar is used as a cement mortar with a ratio of 1.9-2.1 tons of cement Portland cement with a density of 1570-1600 kg / m ³ per 1 m ^{3 of} oil, and oil-cement mortar is discharged with degassed oil until the oil-cement mortar is completely displaced from the wellbore . During technological exposure, the cement cement is diluted with fluids filling the cavity of the cracks. There is a substitution of oil, which closed the oil-cement solution, with produced water. Cement sets and hardens in the part of cracks where formation water is present, and does not set and does not harden in the oil-saturated part of the formation. As a result of such selective action, blocking of cracks from the oil-water channel and below is achieved. The reservoir properties of the oil-saturated part of the reservoir do not deteriorate.

For a more complete filling of cracks in the process of pumping cement, the density of the cement is gradually increased within the above limits.

In addition, the mixture does not solidify in the well. There is no need to drill cement stone or even a cement bridge in the well.

As a result of the operations, it is possible to isolate the fractured part and maintain the permeability of the reservoir.

Concrete example

Drill a deposit 301-303 of the Romashkinskoye field to the level of the Serpukhov overhead horizon. During the construction of wells, deposits of the Serpukhov over-horizon are exploited by an open bottom of limited depth. The wells are tested for inflow by swabbing and the depression of the formation fluid advance is established for the wells that opened the formation without falling into the fractured part, and for the wells that opened the reservoir in the fractured part. It is established that the depression of the propagation of formation fluids through the wells that opened the formation without falling into the fractured portion is 3.5–4.0 MPa, and by the wells that opened the reservoir in the fractured portion — about 0.05 MPa. The injection pressure is set below the depression of the movement of formation fluids through wells that have opened the formation without falling into the fractured part, i.e. below 3.5-4.0 MPa, and with the necessary margin for a range of indicators below 2.5-3.0 MPa. As a cement mortar, an oil-cement mortar is used with a ratio of 1.9-2.1 tons of cement Portland cement with a density of 1570-1600 kg / m ³ per 1 m ^{3 of} oil. The sale of oil-cement mortar is performed by degassed oil until the oil-cement mortar is completely displaced from the wellbore. The volume of injection of oil-cement mortar is 10-20 m ³ . After the cement mortar is poured, technological exposure is carried out under the pressure of the squeeze. On the part of the wells, for a more complete filling of the cracks during the injection of the oil-cement solution, the density of the oil-cement solution is gradually increased.

As a result, the water cut of the extracted products decreased from almost 100% to 10-15%.

The application of the proposed method will improve the efficiency of insulation work.

Claims (2)

1. A method of isolating water inflows or absorption zones in a well, including opening a productive formation by drilling, forcing cement slurry into the annulus and waiting for cement to solidify under pressure in the well, characterized in that, after drilling a section of the reservoir, wells are examined for inflow by swabbing, establishing a depression of progress formation fluids from wells that opened the formation without falling into the fractured part, and from wells that opened the formation in the fractured part, injection of cement p the mortar is kept at a pressure not exceeding the depression depression of the formation fluids through the wells that opened the formation without falling into the fractured part, while a cement-cement mortar is used with a cement-cement mortar with a ratio of 1.9-2.1 tons of cement Portland cement with a density of 1570 per 1 m ³ -1600 kg / m ³ , and the displacement of the oil-cement mortar is performed by degassed oil until the oil-cement mortar is completely displaced from the wellbore. 2. The method according to claim 1, characterized in that during the injection process, the density of the oil-cement mortar is gradually increased.