Method of recovery of casing tightness

 

The invention relates to the oil and gas industry, and in particular to methods for the recovery of casing tightness. Effect: increased efficiency and reduced time of repair and insulation works. In the method of restoring the integrity of casing, including zatvoreniem cement with mineral additives, injection of the obtained cement mixture into the well and displacement with her behind a pillar, as a mineral Supplement use silica or aluminosilicate microspheres, with pre-determined pickup well in the range of leakage and pickup more than 250 m3/day shut cement with the specified additives, and when the displacement of cement mixture in the borehole at a depth of leaks, creating pressure that exceeds the pressure of the collapse of the microspheres. 1 Il.

The invention relates to the oil industry, and specifically to methods for recovery of casing tightness.

Known way to restore the leak tightness of columns, including the preparation and injection well plugging mixtures, including cement, their displacement per column in the interval Nagorny solution thickening or widening of mineral supplements. Therefore, in practice, at high acceleration interval leaks success insulation works does not exceed 20%.

Known way to restore the tightness of casing, comprising preparing the injection well and the displacement of cement per column interval leaks. Moreover, preliminary in cement with mineral additives injected thickening additives, such as sulfite-alcohol bard [2].

The disadvantage of this method lies in the fact that certain additives thickening of cement is already in the process of its preparation. This makes it difficult to pump the mixture from the mixing tank and leads to an increase wellhead pressure already in the initial period of produce composition for the casing. In addition, these additives are inert and do not participate in the hydration process of cement, which ultimately reduces the strength of cement stone.

The aim is to increase the efficiency of the method and reduce the duration of the repair and insulation works in conditions of high acceleration interval leaks.

This object is achieved in that in the method of recovery of casing tightness, vkdwqa her behind a pillar, according to the invention as a mineral Supplement use silica or aluminosilicate microspheres, with pre-determined pickup well in the range of leakage and pickup more than 250 m3/day shut cement with the specified additives, and when the displacement of cement mixture in the borehole at a depth of leaks, creating pressure that exceeds the pressure of the collapse of the microspheres.

In aggregate, the proposed actions allow you to control the process of thickening cement mixture, to obtain a more durable tamping stone in the casing and, ultimately, to improve the efficiency of the method of recovery of casing tightness.

Analysis of the field material is established that the greatest success rate (over 70%) during well cementing cement without additives occurs when the injection well is in the range of 190 to 300 m3/day (see drawing). Maximum success is observed when the pickup 250 m3/day.

In this case, the pickup is the amount of absorbed fluid per unit of time at test wells on the pickup.

When the pickup interval of leakage in the casing which may be necessary in the application of cement mortar with additives silicate or aluminosilicate microspheres.

Silicate (glass) microspheres prepared from a mixture of liquid sodium glass and blowing agent. Hollow glass microspheres have the following advantages: small size, true density, which allows to obtain lightweight materials; low porosity values and the relationship of surface to volume; chemical resistance, flame retardant; stability properties. They in composite materials provide a higher strength than the polymer.

The domestic industry produces hollow glass microspheres brand Of groups A1, A2, A3, B1, B2 and MCO-A9 with a particle size of 200 microns. Differences in physico-mechanical properties of these microspheres is negligible [3].

Thanks mineralogical component composition (SiO2- 78%; Na2O - 8%; CaO - 6%;2About3a 3.5%; ZnO - 2%) this additive is involved in the formation of a cement stone and contributes to the strengthening of its structure.

In primary cementing, mainly conductors, as facilitating additives used hollow silica-alumina microspheres, which are waste combustion in CHP plants or other industries. They are a light friable gray powder composed of separate hollow>and are available on THE 21-22-37-94. Mineralogical composition represented mainly SIO, SIS2- 54,4%; Al2O3- 25,1%; F2About3to 5.8%;2O - 5,4%; CaO - 1,7%; MgO - 1,41%; Na2O - 1,07%. Tensile fracture under hydrostatic compression up to 30 MPa [4].

Cement mortar with the addition of aluminosilicate microspheres, for example? brand ASM-500 when water-cement ratio of 0.5 in normal conditions (pressure of 0.1 MPa, a temperature of 20o(C) has a density of 1.44 g/cm3, flowing down the cone of lubricant additives - 22.5 cm, the start time setting 8 h 10 min Under a pressure of 14 MPa due to the destruction of microspheres the thickening time of the cement slurry at 40% less than that of cement mortar without additives.

The destruction of the microspheres is accompanied by several effects: first, it dramatically increases the density of the cement slurry (to normal), and secondly, the activation of cement due to hydrodynamic microdrop at the collapse of the microspheres (cavitation effect), thirdly, is some heating of the cement due to the transition energy of microdrop in heat, and also due to compression of gas in the microspheres. All of these effects contribute to the rapid salustiano and setting cementa and microspheres by weight may vary from 0.95: 0.05 to 0.50 to:0,50 depending on the capacity of the well, the depth location of the interval leaks. Another ratio of the cement mass and the microspheres or will not allow to receive the effect of the collapse of the microspheres? or will lead to the formation of nizkorodov cement stone.

The proposed method of recovery of casing tightness is as follows.

The perforation interval overlap sandy plug or a cement bridge. Set the location of a leakage in the casing. Determine the acceleration interval leaks and, if it exceeds 250 m3/day, prepare the cement with the addition of silicate or aluminosilicate microspheres, the strength of which failure is determined in advance.

Shut the cement with the addition of microspheres injected into the well, push for casing interval leaks. And at the end of produce cement mixture at the mouth of creating such excess pressure to a depth of leaks developed pressure greater than the collapse pressure of the microspheres.

Backwashing produce cutting cement, lift tubing 100 m and leave the hole waiting for the hardening of cement (RFQ) for 24 h under a pressure of 5-6 MPa.

After 24 h RFQ pressure in column V. the pipe from the well and, if necessary, conduct the planned geophysical research.

To the cement bridge in the area of the defect pillars begin not less than 24 hours after completion of grouting works.

The quality of repair and insulation works (RIRs) check in accordance with the Instruction for the test wells leak".

An example implementation.

Well 1296 Bush 444 Jun-morskogo field NGDU "Surgutneft geophysical methods found that the production column leaks in the depth intervals 1660-1662 and 1690-1693 m

Well choked saline density of 1.17 g/cm3. Determined the injectivity of the well - 700 DOE/day at a pressure of 8 MPa (coefficient pickup - 88 (m3/day MPa). Above the perforated interval set cement bridge.

Prepared 3,3 m3cement mortar with the addition of 20% of aluminosilicate microspheres. Pushed 1.5 m3and crushed 3.4 m3salt solution at an initial pressure of 2 MPa and the ultimate pressure of 11 MPa.

At a depth of 1660 m was reached the pressure of 30.4 MPa (more than the bursting pressure of the microspheres).

Well washed, tubing (tubing) raised to 100 m and the hole left on RFQ - 15 PM

Felt for the bridge at a depth of 1630 m Opressively column pressure of 10 MPa - tightly. SPU is operating column pressure of 9.6 MPa - hermetically.

Thus, the positive effect of the application of the proposed method of recovery of casing tightness in the hole 1296 became apparent that the success of the insulation work has reached 100%. While applying cement mortar without additives at the specified pick-up the success of typically less than 20%, i.e., it requires at least 5 cementing, to ensure the tightness of the column (see drawing).

SOURCES OF INFORMATION 1. RF patent 2116432, M CL E 21 In 33/13, 1998.

2. Amirov A. D., Batanov S. T., Yashin A. S. overhaul of oil and gas wells. - M.: Nedra. - S. 203, 253-257 prototype.

3. Frolov A. A. Special backfill materials for separation gassy horizons fields of the Far North. - Izv. Universities, Oil and gas, 2000, 5, TGHU, Tyumen. - S. 23-30.

4. Frolov A. A., Ovchinnikov, P. C., Valov centuries the Improvement of technologies and technical means for cementing wells in the Far North. - Izv. Universities, Oil and gas, 2000, 5, TGHU, Tyumen. - S. 38-43.

Claims

Method of recovery of casing tightness, including zatvoreniem cement with mineral additives, injection received tamponage ilicate or aluminosilicate microspheres, when this pre-determined pickup well in the range of leakage and, when the pickup more than 250 m3/day, shut the cement with the specified additives, and when the displacement of cement mixture in the borehole at a depth of leaks, creating pressure that exceeds the pressure of the collapse of the microspheres.

 

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