RU2278243C2 - Method for remedial cementing works performing after hydraulic formation fracturing - Google Patents

Abstract

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

SUBSTANCE: method involves temporarily isolating productive bed within low filtration resistance interval by cement bridge forming along with cement forcing in productive formation, wherein cement volume is determined from productive formation thickness, lengths of perforation holes in productive formation and width of cracks created by hydraulic fracturing operation; eliminating water influx from water-bearing seam of underlaying productive formation; perforating impermeable layer, which separates water-bearing seam and productive formation; injecting cement mortar with expansion agent through perforation orifices formed in the layer; drilling cement bridge and creating low filtration resistance channels between productive formation and well by performing repeated productive formation perforation.

EFFECT: increased efficiency and quality.

1 dwg

Description

The invention relates to the oil and gas industry and can be used in repair and insulation works (RIR) to isolate annular flows from an aquifer lying below a productive one after hydraulic fracturing in a casing of oil and gas wells.

A known method of isolating annular flows from an aquifer in a production well, including pumping cement into it through perforating longitudinal slots located in the aquifer, installing a cement bridge in the interval of longitudinal slots with crushing cement into the reservoir (RU 2191886 C2, 10.27.2002) .

The disadvantage of this method is that the perforations of the reservoir are not isolated, and when the cement slurry is injected, it penetrates both the aquifer and the reservoir. At the same time, the hydrocarbon is displaced in the reservoir and the bottomhole zone of the formation itself and the fracture are fractured, which affects not only the flow of water into the well, but also the oil flow rate.

The technical result of the invention is to increase the efficiency and quality of repair and insulation work in wells after hydraulic fracturing of the reservoir.

The specified technical result is achieved by the fact that in the method of repair and insulation work on the isolation of annular flows from an aquifer lying below the productive, after hydraulic fracturing of the reservoir in the oil and gas wells cased by the production string, including perforation of the reservoir lying below the productive and liquidation of water inflow from the aquifer, lying below the productive, before perforating the reservoir, lying below the productive, carry out a temporary shutdown of the productive formation by blocking its channels of low filtration resistance, such as perforations. In addition, to overlap the reservoir in the interval of channels of low filtration resistance, a cement bridge is installed with cement crushed into the reservoir, the volume of cement for filling the reservoir is determined from the condition of the subsequent possibility of creating channels of low filtration resistance between the reservoir and the well.

The creation of an impermeable screen in the channels of low filtration resistance of the reservoir will allow for repair and insulating work without penetration of the grouting mortar into the reservoir, which will affect the injection of grouting mortar with high pressure and allow the mortar to evenly penetrate the entire length of the crack in the cement stone, and also preserve permeability in the fracture and in the bottomhole formation zone. This in turn will affect the necessary effect of both repair and insulation work, as well as from hydraulic fracturing of the reservoir.

The method is illustrated by the drawing, where the drawing shows a diagram of the installed impermeable screen in the reservoir and carrying out repair and insulation work.

The numbers on the diagram indicate:

1 - impermeable layer lying above the reservoir;

2 - reservoir;

3 - impermeable layer lying below the reservoir;

4 - aquifer;

5 - packer;

6 - plugging solution;

7 - impermeable screen;

8 - crack in the cement stone.

Overlapping can be achieved as follows: in the channels of low filtration resistances of the reservoir, an impermeable screen is installed (for example, a cement bridge with crushing of cement into the reservoir, while the volume of cement for crushing into the reservoir is determined from the condition of the subsequent possibility of creating channels of low filtration resistances between the reservoir and well). Then perforate the formation located below the productive (for example, an impermeable layer located between the productive and aquifers) and through the perforations carry out repair and insulation work to isolate water inflow from the aquifer.

This method was carried out at two wells of the Samotlor field, and a positive result was obtained. So, for example, well No. 77204 was drilled in December 2003. After hydraulic fracturing, an inflow of liquid was obtained with a flow rate of 400 m ³ / day and a water cut of 97%. Neighboring wells in this formation No. 77227, 77205, 77083 are operated with water cut from 0.5% to 3%. According to field and geophysical studies, it was found that the design formation is working, and annular circulation from the aquifer lying below the productive one, which is separated from the productive by an impenetrable layer with a thickness of 2.5 m, is noted. To temporarily shut off the productive formation, cement was poured with cement in the formation and leaving a cement bridge. The volume of cement to be pushed into the formation was selected based on the creation of an impermeable screen in the bottomhole formation zone (PZP) with the subsequent possibility of penetration of charges during repeated perforation of this interval, that is, the creation of channels of low filtration resistance between the reservoir and the well. The volume determined by the thickness of the oil-saturated formation (20 meters), the length of the perforation holes formed before the hydraulic fracturing of the formation (0.4 meters) and the width of the fracture in the near-well zone of the well (0.01 meters according to computer simulation of this operation in the MFrac program) was optimal, and amounted to 0.2 m ³ . After waiting for the hardening of cement (OZZ), the cement bridge was pressed with a pressure of P = 150 atm. - tightly. After drilling the cement bridge, the production casing was pressure tested with a pressure of P = 100 atm. - tightly. The perforator PC 105-7 perforated the impermeable layer lying below the reservoir, and carried out repair and insulation work with the injection of cement with an expanding additive in a volume of V = 4 m ³ at an initial pressure P _beginning = 55 atm; final pressure P _con = 130 atm. After the OZC, the production casing was pressure tested with a pressure of P = 150 atm. - tightly. Produced crevice perforation of the reservoir and caused an influx. The analysis showed a decrease in water cut to 12%, with a fluid flow rate of 220 m ³ / day.

Claims (1)

The method of repair and insulation works after hydraulic fracturing of the reservoir to obtain an influx of reservoir products, including temporarily shutting off the reservoir in the channel range of low filtration resistances by installing a cement bridge with crushing cement into the reservoir in a volume determined by the thickness of the reservoir, the length of the perforations in the reservoir and the width of the hydraulic fracture, liquidation of water inflow from the aquifer lying on the producing formation through the perforations impermeable seam separating from the productive aquifer, and pumping the cement slurry with a spreading additive seam through perforations, drilling out the cement plug, creating channels of low filtration resistance between the productive formation and the well bore re perforation of the producing formation.