RU2161239C1 - Method of constructing well of multilayer oil field - Google Patents

Abstract

FIELD: oil-producing industry; methods of well construction in multilayer oil filed. SUBSTANCE: method provides for drilling well to planned depth, lowering of casing string and its cementing. After drilling-in of the first oil layer, well is cased. Then well drilling is continued by bit of smaller diameter to drill-in the other producing layers with subsequent cementing of drilled part of well. The last pipes of casing liner passing the first oil-bearing layer are selected from easily drilled material, for instance, glass-reinforced plastic. Prior to well cementing, installed against producing layer is disconnector which is lowered into well as casing string component with subsequent cementing of well disconnected part under or above the disconnector. EFFECT: preserved reservoir properties of producing layer. 2 dwg

Description

 The invention relates to the oil and gas industry, and in particular to methods for constructing a well of a multilayer oil field.

 There is a known method of completing well construction, including drilling a well to the design depth, injecting a solution with chemically active components into the interval of the producing formation that is neutral to the filtration properties of the producing formation, perforating the latter with explosive perforators, lowering the production casing and cementing (1). In this case, a solution that is neutral to the filtration properties of the reservoir, filling the pores and channels of the reservoir, protects the reservoir from the contaminating action of the fluid, the filtrates of the cement slurry and its hydration products.

 However, the known method, having progressiveness, has several disadvantages. For example, it is not applicable in the construction of wells of a multilayer oil field. This is explained by the fact that when drilling a well of a multilayer oil field, if it is used in the first oil formation discovered by drilling, the neutral solution is pumped in with the subsequent continuation of drilling under the influence of alternating pressure in the well, the solution protecting the formation from pollution goes back out of the channels and pores of the reservoir and therefore ceases to fulfill its protective properties. In addition, the method is complex and not technologically advanced. It requires calling a geophysical batch for lumbago, strict compliance with the weight ratios of the components of the composition, preparation, delivery to the well.

 The closest analogue of the invention is a method of constructing a well of a multilayer oil field, including drilling a well to the design depth, lowering the production string and cementing it (2).

 This method is applicable in the construction of wells of a multilayer oil field in order to protect against pollution of productive formations. When using this method, the presence of an additional steel shell causes a number of difficulties associated with the secondary opening of the reservoir - when creating a hydrodynamic connection between the reservoir and the well.

 This is explained by the fact that the creation of an additional barrier - the installation of a steel shell opposite the productive formation leads to a decrease in the efficiency and quality of opening when using conventional perforators. Therefore, there is a need to create more powerful cumulative perforators. The use of which would also lead to a violation of the integrity of the cement stone behind the column. In addition, the installation of a steel shell opposite the reservoir requires complex equipment and is associated with an unjustified large expenditure of time of drilling crews.

 Further, drilling a well with a bit of one diameter to the design depth in a multilayer field leads to severe contamination of the previously discovered oil-bearing formations during drilling with mud filtrates and cement filtrates, as well as cement hydration products, under the influence of large pressure drops, during drilling - mud columns, and during cementing - cement.

 The technical result of the invention is to provide a method for constructing a well for a multilayer oil field, providing maximum preservation of the reservoir properties of the upper (upper) productive formation based on traditional and progressive well construction methods.

 The necessary technical result is achieved by the fact that according to the method of constructing a well of a multilayer oil field, including drilling a well to the design depth, lowering the production string and cementing it, according to the invention, after the drilling of the first oil reservoir, the well is fixed by installing a disconnector opposite to the producing reservoir, run in the composition the casing string, followed by cementing the separated part of the well, continue with a bit of smaller diameter, revealing the rest of the production tive layers, followed by cementing the drilled portion of the well, the latter pipe liner production casing extending opposite the productive layer selected from legkorazburivaemogo material, for example, of fiberglass.

 Figure 1 shows a well in longitudinal section, where it can be seen that the first oil-bearing formation was opened by drilling with a bit of one diameter, and the others with a bit of a smaller diameter, the first and last productive layers are protected from contact with the cement mortar by disconnectors, which form voids in the annulus opposite these layers . Figure 2 is a section along aa of figure 1.

 The method is carried out in the following sequence.

 Drilling open the first oil reservoir 1 (see figure 1) of industrial importance with a bit of one diameter. As a part of the casing 2, a disconnector is lowered with packer elements 3 and 4 with cementing tubes 5 passed through them, and set it opposite the reservoir. As such a disconnector, devices can be used to protect the reservoir from contamination during cementing of a device of the type "USIP" or described in the patent of R.F. N 2091564, CL E 21 B 33/14, published. in B.I. N 27, 97, containing the same structural elements as noted above.

 After putting the packing elements into position, the well 6 is cemented using the traditional method using cementing aggregates. The cement mortar through the shoe of the casing enters the annulus, fills it and, having reached the lower packer element, rises up and fills the annulus above the upper packer element 3 through the cementing tubes 5 of the isolator, without contacting the productive formation 3. Thus, the productive formation is protected from cement slurry, its filtrate and cement hydration products, which are reservoir mud, causing great difficulties in well development.

 The necessity of cementing the drilled part of the well after opening the first productive formation by drilling is dictated by the fact that, with continued drilling to reach the design depth, this formation is heavily contaminated with drilling fluid filtrates, as well as various process and plugging fluids during well drilling. Under the influence of large pressure drops in the well, they penetrate deep into the reservoir, forming a strong mud layer, difficult to clean. In addition, as the practice of developing the Romashkinskoye oil field in Tatarstan has shown, all of the above-mentioned pollution factors of the reservoir are enhanced by the fact that the reservoir pressure of the upper horizons is much lower than the lower ones, and the drilling fluid for drilling is selected based on the maximum pressure in the well.

 Then, the well is continued to be drilled with a bit of smaller diameter to the design depth, revealing the existing productive formations in sections 7. Then the pipe string, the so-called “liner” of the production string, is lowered into the drilled part of the well with a margin so that the last pipes 8 of the shank 9 of the production string cover the interval first productive formation 1. These pipes 8 are selected from easily drilled material, for example, from fiberglass, in Fig. 1 fiberglass pipes are depicted by dash-dotted lines. The need for a fiberglass pipe as a part of the shank is dictated by the fact that it is easier to drill, can be processed without complications.

 Cement the liner 9 of the production casing by conventional technology, similarly to that described above, if necessary protecting the productive formations of the lower horizons from the contaminating effects of the cement, using, for example, 2-stage cementing, or pushing the cement from the interval of the productive formations with rubber-fabric sleeves (see and.with. N 1765372, cl. E 21 B 43/11, published in B.I. N 36, 92), or having applied the device like "USIP".

 After completing the process of selling the estimated volume of cement, the upper part of the pipe string is disconnected from the fiberglass pipes 8 and raised to the surface.

 The transition to drilling with a drill bit of a smaller diameter is carried out in order to protect the upper productive formations from the contaminating effects of drilling fluids, etc., since under drilling conditions with a pressure difference between the upper and lower productive formations, the upper formations (they have a lower formation pressure) are more prone to contamination drilling and cement mortars.

 The development of such wells with several productive formations is carried out according to the traditional system, starting from the lower layer. After the development of the lower productive strata, the operation of the upper productive stratum begins, after a preliminary shutdown of the lower strata by installation of cement bridges and drilling of fiberglass pipes.

 The technical and economic advantage of the proposal is as follows.

 Compared with the traditional (basic) well construction technology, the proposed method leads to much less pollution of productive formations having different reservoir pressures, which makes it possible to preserve their reservoir properties, reduce well development time with minimal labor and energy costs, and increase reservoir productivity. In addition, the use of the method will reduce the cost of material resources - metal, cement, etc.

 The widespread use of the method in the oil fields will provide tangible economic benefits.

Sources of information
1. RU 2061837 C1, 06/10/1996.

 2. SU 911 015 A, 03/07/1982.

Claims (1)

 A method of constructing a well of a multilayer oil field, including drilling the well to the design depth, lowering the production string and cementing it, characterized in that after opening the first oil formation by drilling, the well is fastened by installing a disconnector opposite the productive formation, run in the casing, followed by cementing the fragmented parts of the well beneath and above the disconnector, then the drilling of the well continues with a bit of smaller diameter, revealing the remaining productive formations followed by cementing the drilled portion of the well, the latter pipe liner production casing extending opposite the first productive formation, selected from legkorazburivaemogo material such as fiberglass.

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