RU2211301C2 - Method of wellbore treatment - Google Patents

Abstract

FIELD: construction of wells of various application, particularly, drilling and completion of oil and gas wells. SUBSTANCE: method includes supply of hydraulic pressure jets of mud onto well walls in course of well drilling. Introduced into mud is portland cement with concentration of 7-50 wt. % for formation of cemented wellbore screen 20-30 mm deep. Said screen provides for wellbore sealing under repression of 15 Mpa and depression of 15 Mpa. EFFECT: increased efficiency of isolation of well permeable walls. 1 ex

Description

 The present invention relates to the oil and gas industry, namely the isolation of permeable rocks when drilling wells for various purposes.

 Most of the complications and accidents during well construction are due to the opening of permeable formations, which leads to liquid absorption, disruption of drilling technology, as well as gas and oil manifestations and emissions.

 There is a method of intensifying the progress of colmatization of low porous permeable rocks by a mechanical method (Kurochkin B.M. et al. Intensification of the process of colmatizing finely porous permeable rocks by a mechanical method. —NTZh Oil Industry, 1973, 6, pp. 11-13). The essence of the method is to treat the walls of the borehole with metal brushes while rotating the drill string and moving it in the processing interval using a special device installed above the bit. The disadvantages of the method include the low efficiency of the mud process, the duration of the operation, which is incompatible with the drilling process, the need to use a special bulky device design, and the possibility of its use only in the intervals of the barrel with a nominal bit diameter. At the same time, in the near-well zone of the well, a mud layer is formed with a thickness of not more than 10-12 mm with low waterproofing and strength characteristics, which are completely disrupted by repressions of 4-5 MPa and depressions of 0.3-0.6 MPa.

 Closest to the proposed method in technical essence is a method of reducing the permeability of formations (as USSR 819306, class 3 E 21 B 33/138, 1981) by treating the wellbore with hydro-monitor streams of clay mud during drilling through a nozzle installed in a supra-bit sub at a flow rate of 60-120 m / s.

 Significant disadvantages of the method include the limited hydromechanical strength of the formation layer in the near-barrel zone, the violation of which occurs under the action of depression, not exceeding 4-6 MPa.

 To increase the efficiency and quality of waterproofing permeable rocks from the wellbore during drilling, the permeable walls are treated with jetting jets of washing fluid with the introduction of Portland cement with a concentration of 7-50 wt.% Into the washing fluid, while the speed of the jetting jet is changed from 20 to 150 m / s .

 An example implementation of the method.

At the opening of the productive stratum in the well 3842 "3" of Pavlovskaya area, NGDU "Aznakaevskneft" by the rotary method, 50 wt. % of Portland cement, 0.1 PAA (polyacrylamide) and 2.0 (wt.%) KSSB, and the parameters of the flushing fluid are given in accordance with the requirements of the design specification (geological engineering work): density 1070-1090 kg / m, nominal viscosity 30 s, water loss 15 cm ^3/30 min. The layout of the bottom of the tool included: bit Ш - 125 ТК3цв., Over-bit sub with one nozzle with a diameter of 10 mm, drill collar - 24 m further on the drill pipe string. The processing mode of the walls of the well with hydro-monitor jets of flushing fluid: the velocity of the fluid stream is 90 m / s, the bit rotation frequency is 1.0 s, the tool speed is 6-12 m / h.

 As the hydromechanical tests of the wellbore in the processing interval showed, at a depth of cemented borehole screen of 20-30 mm (established by analysis of the core taken from the walls of the well with a drilling core sampler during the second opening of the oil-saturated formation), the tightness of the bore was not broken when creating a repression of 15 MPa and a depression of 15 MPa .

The main advantages of the method include:
high waterproofing characteristics of the protective screen formed in the near-wellbore zone, consisting of a cemented stone and a crust layer on the surface of the trunk, providing reliable insulation of permeable and hardening of unstable and prone to hydraulic fracturing rocks;
the wide possibilities of the method for facilitating and simplifying well designs, non-metallic wellbore fastening, completion of wells with open bottom, preservation of the natural reservoir properties of productive formations and potential well productivity.

 The implementation of the noted advantages of the method provides reliable long-term tightness of the lining, preserves the potential productivity of the wells, significantly increases the anhydrous period of operation and creates optimal hydrodynamic conditions for the treatment of bottom-hole formation zones (EOR), the use of methods to increase oil recovery (EOR) and the repair and insulation works (RIR) ) during the operation of wells.

 As the results of field trials of the proposed method showed, the well production rate increased by 1.5-3.0 times compared to traditional well completion methods, the water cut of oil decreased by 75-100%, the cost and time spent on conducting RIRs were reduced by 3-10 times .

Claims (1)

 A method of treating a wellbore by supplying jetting jets of flushing fluid to the walls of the well during drilling, characterized in that Portland cement with a concentration of 7-50 weight is added to the flushing fluid. % for the formation in the processing interval of the cemented near-barrel screen with a depth of 20-30 mm, ensuring the tightness of the wellbore with repression of 15 MPa and depression of 15 MPa.