How well killing

 

The invention relates to the oil and petroleum industry, and more specifically to the operation of wells, and can be used, for example, the repair of wells. In the way of plugging wells comprising introducing into the wellbore a viscoelastic barrier composition, preparation and injection into the borehole fluid damping with targeted supplements to balance the pressure of the reservoir, as well kill fluid using an aqueous solution of carnallite ore density of a solution of 1.23-1.25 t/m3as a thickener - xanthan resin in an amount of 0.1 to 1.0 wt.%, and in the preparation of the specified solution is performed sucks within 30-45 minutes the Technical result is the preservation of reservoir properties of the bottomhole zone. table 2.

The invention relates to the oil and petroleum industry, and more specifically to the operation of wells, and can be used, for example, the repair of wells.

There is a method of plugging wells in which the well bore is injected kill fluid to balance the pressure of the reservoir, as well kill fluid use produced water [1].

This method has the disadvantage of the CET subsequent continuous operation of the well.

There is also known a method of plugging wells in which the well bore is injected viscoelastic release agent, and then prepare, defend, heated and pumped into the well kill fluid to balance the pressure of the reservoir, as well kill fluid using an aqueous solution of sodium chloride [2].

The disadvantage of this method is the loss of reservoir properties of the bottomhole zone of the reservoir in the swelling of clay particles in the reservoir and respectively overlapping channels, which receives the extracted fluid (oil, gas mixture or gas and so on).

Closest to the claimed technical solution in its essence and the achieved technical result is a method of killing the well, wherein the well bore is injected viscoelastic release agent, and then prepare, defend, heated and pumped into the well kill fluid to balance the pressure of the reservoir, as well kill fluid use natural binary system - Silvinit [3].

The disadvantage of this method is the loss of reservoir properties of the bottomhole zone of the reservoir is not so much a result of the neb is Yes (oil, oil and gas or gas mixture, and so on), particles of insoluble impurities, which in Silvinit contains up to 3-5%.

Conducted by the applicant's analysis of the prior art, including searching by the patent and scientific and technical information sources and identify sources that contain information about the equivalents of the claimed invention, has allowed to establish that the applicant is not detected similar, characterized by signs, identical to all the essential features of the claimed invention, and the definition from the list of identified unique prototype, as the most similar set of features analogue, has identified a set of essential towards perceived by the applicant to the technical result of the distinctive features of the claimed object set forth in the claims.

To check the compliance of the claimed invention to the requirement of inventive step, the applicant conducted an additional search of the known solutions in order to identify characteristics that match the distinctive features of the prototype of the claimed invention, the results of which show that the claimed invention is not obvious from the prior art, a particular applicant identified the influence of the preamplifiers is the result.

The aim of the invention is the preservation of reservoir properties area by reducing the negative impacts of insoluble impurities.

Summary of the invention in a method of plugging wells comprising introducing into the wellbore a viscoelastic barrier composition, preparation and injection into the well kill fluid with additives inhibitors sludging and corrosion, surfactant and thickener for balancing the pressure of the reservoir, used as a kill fluid aqueous solution of carnallite ore density of a solution of 1.23-1.25 t/m3as a thickener - xanthan resin in an amount of 0.1 to 1.0 wt.%, and in the preparation of the specified solution is performed sucks for 30-45 minutes

It is known that killing the well is mostly for maintenance and repair work. Task killing is the suspension of production fluid from the well, however with the difference that the flow rate of the well after completion of the relevant work has remained unchanged (for perforation flow rate should even increase).

The complexity of the task of killing widely described in the literature and not Nugroho solution from the well kill fluid, as contained in the first target additive - various reagents, additives, inhibitors, antiflatulent and so on , contact salt solution which may lead to loss of well failure.

The second is the removal of the sludge by mixing the kill fluid with formation waters of varying degrees of salinity. The third is the exception corrosion of the metal equipment wells saline - kill fluid, especially given the temperatures and pressures developing in deep wells.

The first aspect of the problem is solved by introducing into the wellbore a kind of "tube" in the form of a viscoelastic barrier composition, insulating drilling fluid from contact with the fluid damping. At the same time as the specified separator composition using aqueous solutions of cross-linked polyacrylamide. The decision of the second aspect of the problem is the most difficult.

The most simple in this case is the use of salt solutions of high purity, for example calcium chloride. However, the economic feasibility of such use in all cases is highly questionable. In practice, the kill fluid based on mineral salts are prepared in a special resesarch (10-12) hours, and in special containers delivered directly to the well, where is heated to temperature in the wellbore and only then pumped into the well. Use as a kill fluid aqueous binary systems, such as sylvinite, does not ensure the preservation of reservoir properties in the area, and the use of raw and unprepared mixtures as the basis of killing fluids leads to unnecessary complication of the technology and increase the risk of late effects - for example the failure of deep pumps, etc. in Addition, the risk of precipitation upon contact of the kill fluid with formation waters in this case is very high. Modern technology helps to minimize this risk by the introduction of inhibitors of the precipitation. As these inhibitors are most often used nitrilotriethanol acid (NTF) or inhibitor snpch - 5301 M (the product of the interaction of oksietilidendifosfonovaya acid with aqueous ammonia in the presence of high-boiling fractions (M-2) products of petroleum refining).

To improve the rheological characteristics of the kill fluid is injected thickeners, such as polyacrylamide.

The third aspect of the problem of killing the well technically solved by the introduction of liquid glue is And - 1 - A.

According to the applicant the use of the ternary system, and carnallite: sodium chloride (~ 20%) - magnesium chloride (~25%) - potassium chloride (~22%) of crystallization water (rest), is one and the same natural origin, brings an unexpected effect. The ternary system (meaning an aqueous solution of a mixture of three salts), as will be shown below, have advantages in comparison with dual solubility, stability system, density characteristics, and the almost complete absence of insoluble impurities in the proposed triple system makes it most suitable for use as the basis for preparation of the kill fluid. Physico-chemical characteristics of carnallite, especially the solubility and concomitant dissolution phenomena such as dissolution rate, thermal effects, the density of the solution and, what is especially significant, the almost complete absence of insoluble impurities makes it most suitable for use as the basis for the preparation of the kill fluid, and this fluid can be prepared directly from the wells, and the technology of preparation of liquid requires basically no stage of otstaivaniia as a thickener also brings the element of surprise. The rheological characteristics of the fluid damping in the introduction to her even a negligible amount specified resins vary sharply - formed a gelatinous system in which migration even accidentally trapped insoluble impurities is virtually absent, and hence there is no penetration of the impurity particles and the fluid damping in the bottom zone.

As mineral salts for the preparation of the kill fluid is used carnallite - natural ternary system NaCl-MgCl-KCl. As a viscoelastic barrier composition using aqueous solutions of cross-linked polyacrylamide.

As the precipitation inhibitor use nitrilotriethanol acid (NTF) or inhibitor snpch - M.

As a corrosion inhibitor, a mixture of several substances called And - 1 - A.

As the surfactant used neonol AF-12, OP-7, etc.

As a thickener use xanthan resin (high molecular weight polysaccharide complex composition, produced by "Rhone Poulenc, France).

For professionals certainly evident that the main functional features of the kill fluid is the creation of back pressure, but rather the balancing of the pressure in the well. This stami the following order (see table 1).

For a better understanding of the claimed technical solution can be illustrated by, but is not exhausted by the following specific examples of its implementation.

Example 1 carried out the killing of well 47/5 Montenegrin oil field (Nizhnevartovsk oil and gas province). Daily well production rate is 27.5 so the depth of the well to the productive formation is 1570 m Temperature in the wellbore in the area of the productive formation is 105oC. Pressure ~195 ATM. Kill fluid is prepared by dissolving powdered carnallite ore in water at the rate of 600 kg of carnallite 1 m3water. The solution also impose 5 kg xanthan resin, 1.3 kg of inhibitor - 1, 2.5 kg of Neonols AF 9-12 and 4.5 kg of precipitation inhibitor snpch-M. Defending ready for the kill fluids are within 30 minutes Then, well put 100 l viscoelastic barrier composition on the basis of the solution of the polyamide and then hold killing the well by pumping prepared liquid. After complete displacement of the drilling mud fluid damping replace the downhole pump and then replace the kill fluid mud in reverse order. Then resume oil production. Dean carried out as in example 1, except that the change in the composition of the components and some of the modes. Technological methods of killing, killing fluids, as well as comparative example and the results are shown in table 2.

As seen from the above examples, including comparative, using carnallite as the basis of the kill fluid and xanthan gum as a thickener allows you to save the reservoir properties of the bottomhole zone.

Sources of information 1. RF patent 2096591, CL E 21 In 43/12, 20.11.97.

2. Ryabokon S. A. and other Fluid damping for repair of wells and their influence on reservoir properties of the formation. M, VNIIEM, 1989, ser. Petroleum engineering, vol. 19, S. 3.

3. RF patent 2169832, CL E 21 In 43/02, 27.06.20001.

Claims

Method of plugging wells comprising introducing into the wellbore a viscoelastic barrier composition, preparation and injection into the well kill fluid with additives inhibitors sludging and corrosion, surfactant and thickener for balancing the pressure of the reservoir, characterized in that used as the kill fluid aqueous solution of carnallite ore density of a solution of 1.23-1.25 t/m3syshestvyut sucks for 30-45 minutes

 

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