RU2016188C1 - Method for oil and gas well casing cementing - Google Patents

Abstract

FIELD: oil and gas producing industry. SUBSTANCE: technical, economical and ecological deep well completion level is increased by improving the degree of substitution of drilling mud by plugging solution and by creation, during second section cementing, of a filtration preventing barrier of waste drilling mud in formations saturated by saline waters. EFFECT: increased efficiency of the process.

Description

 The invention relates to the mining industry and can be applied when drilling wells for oil and gas, especially when drilling deep exploration wells.

 Sectional casing descent is predetermined by the rig's carrying capacity or by the limitations in the physicomechanical characteristics of the casing and consists in lowering the casing in parts (sections) and cementing them using direct circulation.

 An essential method of cementing sectional casing strings (1) does not allow burial of spent drilling mud (OBR) when cementing sectional casing strings, creating a hydraulic screen between the cement ring and the formation saturated with formation water or high-pressure brine. The existing method of cementing sectional casing strings is similar to that proposed by only filling the annular and annular spaces with cement slurry. When cementing the first section in the traditional way, after cutting off the excess cement slurry and unloading the section onto the structure of the cement stone, the II section descends and cementing is performed. The proposed method after the descent of the I section and its cementing and after the descent of the II section provides for the expectation of hardening of the cement slurry only in the lower part of the I section. After this, absorption is caused in the permeable formation, which allows to discharge the OBR, bury it in the formation through the annulus and cement the interval of the column to the upper part of section 1, section II to the wellhead by backfill for absorption.

The disadvantages of the analogue are as follows:
- there is no directed active effect on water-saturated horizons that can act on the emerging cement ring and cause fluid flows through the cemented space. This disadvantage is eliminated by the proposed method.

 The purpose of the invention is to maintain the quality of the opening of productive sediments, reducing the repression of cement slurry on them; to increase the reliability of the cementing process of the I section, by reducing the volume of cement slurry, which is especially important when using stale cements or cements containing sediment dispersed fillers; Section II due to the exclusion of the process of selling cement slurry; ensure isolation of formations in the lower part of the well by creating anti-filter screens from OBR in formations with highly saline water and increase the ecological level of drilling operations when completing wells by burial of OBR in deep-seated formations.

 The method is carried out in such a sequence.

 The upper end of section 1 is located above the productive stratum in a section of a well with a nominal diameter, it is well centered, and the section is cemented with two portions of grouting mortar with different setting times with the addition of a larger amount of moderator (structurant) in 1 portion. The first portion replaces the drilling fluid in the interval of the docking unit - the sole of the upper waters of the productive horizon.

Then, the well is washed from the top of 1 portion of the cement slurry l _cr above the docking device and the drill string is removed from the well. After lowering the casing and the end of setting of the II portion of the grout, the absorption is restored (or caused) by increasing the pressure in the annulus. The absorption interval is determined by the device, which is located in the column and fixes the circulation of the drilling fluid in the annulus.

 After establishing a hydraulic connection with the absorption zone below the docking device, OBR and liquid industrial waste are pumped into it, and cementing of the II section and the upper part of the I section of the column is ended by selling cement slurry to the absorption zone.

For better injectivity, the absorption zones resort to the action of hydromechanical resonance through the column on the formation (2). It also allows you to prepare the crust of the drilling fluid for better flushing from the walls of the well and a more complete replacement of the drilling fluid with grouting. The injection into reservoirs with highly mineralized water of a larger amount of OBR from 100 to 250 m ³ allows you to push the fluid from the well and create an anti-filter screen, which allows you to protect the cement ring from penetration of brine or gas during its formation, as well as during development and operation of the well.

 The proposed technology allows to increase the technical and economic level of drilling operations and the reliability of determining prospected reserves with a significant reduction in the cost of reclamation of disturbed lands during exploration for oil and gas and is recommended for use both in the Far North and when drilling deep wells in other areas.

 The method is as follows.

 PRI me R. The descent of the first section of the production casing to 5000 m. The first stage of cementing (1e) with two portions of the grouting mortar (1 p and II p) by direct circulation. The difference in the setting time between the portions in their upper part is not less than the time required for pumping fluid (a) into the pipes, lifting the drill pipe string (b), lowering the casing string section II, establishing a hydraulic connection with the PP absorbing layer through the annulus (in ) I p cement slurry in the interval of slaughter - the roof of the productive horizon contains retarders (CMC, PAA for cement or dispersed fillers, NTF for cement with Gost's dispersion), II p contains a reduced dosage of retarder. After receiving the “Stop” check the check valve for leaks.

Before lifting the drill string flush the upper part of I p cement slurry l _cr . After raising the drill string, lowering the second section II c and articulating the sections with the US docking device, the control device for drilling fluid circulation in the annulus to the depth of the proposed absorbing horizon is lowered into the string, the absorption is induced (c), forcing the remnants I p enclosed between the sole into the formation upper formation water and the head of the I section, drilling fluid in the annulus behind the II section, spent drilling fluid (OBR) and liquid industrial waste accumulated at the drilling site. Then the cement grout (TR) is injected into the annulus to the absorption zone (d).

Claims (1)

 METHOD FOR CEMENTING CASING OIL AND GAS WELLS, including casing running, pumping cement slurry by direct circulation to the absorption zone, restoring the absorption in permeable formations with drilling fluid by creating pressure on the wellhead, followed by pumping the spent drilling fluid through the annulus into the absorbing formation (Ob drilling fluid) and injecting backfill of cement slurry with reverse circulation from the mouth to the absorption zone, characterized in that, in order to maintain the quality of opening, it is productive reservoirs, to increase the reliability of cementing deep wells, to ensure the quality of isolation of reservoirs in the productive part of the well and the disposal of OBR in deeply absorbing reservoirs, the casing is run in two sections with the docking unit above the absorbing reservoir, the grouting solution is injected to the absorption zone in two portions , one of which with a slower setting time is located in the interval of the docking unit - the bottom of the absorbing layer, and the restoration of absorption after blowing off OBR is performed before the expiration of the loss of pumpability of a portion of the cement slurry with a delayed setting time.