SU994689A1 - Method of isolating permeable formations in a well - Google Patents

Description

The invention relates to the drilling and operation of wells for various purposes, in particular, to the technology of isolating permeable formations in open or cased shafts.

A known method of isolating permeable formations in wells involves filling the wellbore in the interval of the insulated formation with a hydraulic fluid and mechanically destroying filter crusts on the walls of the trunk to ensure intensive and deep penetration of this solution into the l3 formation channels. The disadvantage of this method is the impossibility of applying it is used to isolate layers in cavernous sections of the trunk and layers represented by weakly cemented rocks. The inefficiency of the method in the first case is caused by the limited length of the scraper elements, and secondly by the destruction of the rock under the influence of the scrapers.

Closest to the present invention is a method of isolating permeable formations in wells by pumping into them a cement slurry under pressure above reservoir C 21.

The disadvantages of this method are the low efficiency of isolation of the layers in the cavernous sections of the trunk and the impossibility of using it to isolate weakly cemented rocks; the productivity of insulation works is low, since only sections of the trunk are subjected to treatment, the direct impact of pressure in places of the lowest strength of rocks is tested. This forces long-term interval processing of the walls within the limits of the entire insulated formation.

15

The purpose of the invention is to increase the effectiveness of the isolation of the formations due to the possibility of processing the insulated formation along its entire height.

The goal is achieved

20 in that, according to the method of isolating permeable formations in wells by pumping a cement slurry under pressure above the reservoir, the pressure is increased cyclically, alternating with decreasing to a value below the reservoir pressure, and in each cycle the pressure increase is exceeded long decline

Claims (2)

30 pressure build-up in each cycle until the beginning of a decrease in the injectivity of the formation and the duration of pressure reduction from cycle to cycle from 5 to 300 s, while the pressure increases to a pressure not higher than the fracturing pressure. The method is implemented as follows. A drill tool equipped in the shoe part with self-sealing elastic cuffs is lowered into the well to the sole of the insulated formation. The tamping fluid is pumped into the barrel, calculated not only in the interval of the reservoir to be isolated, but also higher with a reserve due to the amount of tamponage fluid squeezed into the reservoir. The tool is raised above the cement fluid head, placing the bucket device in the non-vectored. trunk section or in the previously lowered casing string, and begin the process of isolation of the reservoir. To do this, the tool is lifted at a speed that allows achieving a given pressure decrease by the AR, equal V-e) where P is the pressure of the hydrostatic column of flushing fluid at the depths of the insulated reservoir P is the formation pressure; LR./- value of pressure reduction on the formation (depression value), the control over the value of AR is performed using the weight indicator at the rig, Due to the decrease of the bottomhole pressure on the AR under the shoe, the weight of the moving tool increases by DS: Dbd Mz. where D is the nominal diameter of the well. The result of a decrease in pressure below the reservoir is the movement of reservoir fluids in the direction of the well and, in connection with this, detachment from the walls of filtration crusts, which prevent penetration of the cement fluid into the channels of permeable rocks. After the tool is lifted, it is lowered at a speed that provides an increase in bottomhole pressure by the value of CvP: LRG RPK + DRR) - P where LRr is the amount of repression on the formation. In this case, the total bottomhole pressure does not exceed the fracturing pressure of the rocks, and the pressure increase exceeds the value of its decrease relative to the reservoir pressure. The regulated value of DSR was achieved and maintained in orientation to the weight indicator readings. Due to the increase in hydraulic pressure under the tool, the weight on the hook decreases by the magnitude of AGpt. The duration of the pressure increase is determined by the change in reservoir acceleration time, the value of which is proportional to the speed of the tool descent. Injectivity (or the speed of the descent of the tool) acquires a certain value at the beginning of the descent, and as the cementing fluid penetrates into the formation channels, it gradually decreases. However, the penetration of the cementing fluid into the reservoir in the last stage is sharply slowed down due to the formation of a crust on the walls of the well. At the same time, there is a sharp decrease in the speed of the descent of the tool while maintaining the size of the load .uGp. Further exposure to the walls with excess pressure only leads to an increase in the thickness and density of the filter cakes. Therefore, a sharp decrease in the speed of descent serves as a signal for stopping and beginning a subsequent cycle of decreasing and increasing bottomhole pressure. At the final stage of the isolation works, the pickup from the very beginning of the impact on the walls with excess pressure will be minimal (close to zero), which indicates the complete saturation of the channels in the bottomhole formation zone with the cementing fluid i. about the creation in the channels of such a tampon, which is able to withstand excess pressure within a given value of Lr ,. Isolation work always starts, creating depression for the minimum time. Low acceleration or lack of it during the subsequent descent of the tool indicate an insufficient duration of depression. Therefore, from cycle to cycle, the formation time is increased to the occurrence of injectivity sufficient to successfully complete the insulation work. П Р and м.е р. Conditions: the reservoir to be isolated at a depth (H) of 2400 m, formation pressure (Rrd) 240 kgf / cm, density of the fluid filling the well (p) 1.2. borehole diameter, .19 m, depression value (D1) 20 kgf / cm, increase in pressureLenin (APp) -80 kgf / cm, fracture pressure gradient (q) 0.15 kgf / cm m. Main technological parameters of the process isolation: the value of the decrease in the bottomhole pressure lr by the formula (1) (240–20) 68 kgc / cm the magnitude of the increase in the load on the hook (by weight indicator) DSd by the formula (2) 19 dSd 19300 kgf; the magnitude of the increase in the bottomhole pressure of the Republic of Latvia according to the formula (3): A). 32 kgf / cm is the value of the decrease in the load on the ASK hook according to the formula (4):. 9100 kgf; AGp 32 fracture pressure of rocks (Рцр) g 0.15-2400 360 kgf / s bottomhole pressure during the descent of the tool (Pa): l, JJi +., Ц2.2400 + 32. 10 320 kgf / cm. i Thus, the injection of the grouting mixture into the reservoir, rsu1tstvlivatsya at downhole pressures less than the hydraulic fracturing pressure of the rocks. Along with the direct purpose of isolating absorbing or gas-saturated rocks, layers with plantar water, the formation of a high or abnormally low reservoir pressure, the proposed method can be applied to restore the tightness of the annular space through a shoe or perforated site. hermetic breach intervals Positive, the effect of the application of the proposed method is provided by the possibility of isolating plates composed of poorly consolidated rocks or a hall cavernous areas of the well, reducing the time of insulation works, as the walls of the trunk are subjected to hydraulic impact along the entire height of the isolated plast. Moreover, the efficiency of the work increases due to continuous monitoring of the processes of channel saturation and control of these processes. The economic effect per one well is not less than 212.5 thousand rubles. . Claims of the Invention Method, isolating permeable formations in wells by pumping Tc of pumping fluid under pressure above the reservoir into them, so that, in order to increase the isolation efficiency of the formations due to the possibility of treating the insulated formation throughout its height, the pressure is increased cyclically , its sequence with a decrease to a value below the reservoir pressure, and in each cycle it is ensured that the value of the pressure increase exceeds the value of its decrease with the duration of the pressure growth in each Cycle until the beginning of a decrease in the injectivity of the reservoir and the duration of pressure reduction from cycle to cycle from 5 to 300 s, while the pressure is increased to a pressure not higher than the fracture pressure. Sources of information taken into account in the examination 1.Kurochkin BM and others. Intensification of the process of clogging of fine pores by mechanical means. Oil business, No. 8, M ,, Nedra, 1972, pp. 20-28. 2.Krylov V.I. et al., Improving the Zrn Absorption Isolation Technology During Well Drilling, OH, Drilling Series, M., VNIIENG, 1978, p. 14-17.