THE USE OF DUAL COMPLETION FOR THE INTRODUCTION OF PRODUCTIVE HORIZONS AND FOR SOLVING TECHNICAL PROBLEMS OIL AND GAS PRODUCTION
THE USE OF DUAL COMPLETION FOR THE INTRODUCTION OF PRODUCTIVE HORIZONS AND FOR SOLVING TECHNICAL PROBLEMS OIL AND GAS PRODUCTION
Annaguly Deryaev
Candidate of Technical Sciences, Senior Researcher, Scientific Research Institute of Natural Gas of the State Concern „Turkmengas”,
Turkmenistan, Ashgabat
ABSTRACT
With dual completion (DC) of two or more horizons, reservoir development can be carried out according to the following schemes: fountain-fountain; fountain-pump; fountain-gas lift; fountain-injection; gas lift-pump; gas lift-gas lift, gas lift-injection; pump-pump; pump-injection; injection-download. The field experience of the operation of two layers by one well using the DC method indicates its high efficiency.
Keywords: Permeability, saturation, perforation, contour, thermal waters, interpretation, fluid flow.
Depending on the nature of the main indicators that determine the economic efficiency and technical and economic feasibility of transferring wells to dual completion of reservoirs, it can be divided into three main groups:
1) control and regulation of the development process of a multi-layer facility in order to intensify current production and obtain maximum final oil recovery;
2) introduction of new productive facilities to development in production and injection wells in order to obtain additional oil production;
3) the use of dual completion in order to solve technological problems of oil and gas production.
For each of these three groups, there are methods for determining the technical and economic efficiency of dual completion.
The first group of technological tasks can be attributed to the use of dual completion in order to:
a) ensure optimal operation of each of the formations developed jointly (creating conditions for an independent grid of wells for each formation);
b) regulation of the development of the facility for reservoirs having various reservoir properties (uniform production, intensification of selection, restriction of water inflow in one of the reservoirs, extension of the terms of fountain operation of wells, separate collection of clean and watered oil)
The second group of technological tasks – the introduction of new productive objects to operation in working wells - can include the use of DC for the purpose of:
a) the introduction (perforation) of productive formations in conservation;
b) compaction of the grid of production or injection wells for one of the operated objects of a multi-layer field;
c) connecting lenses and dead-end zones of one of the operational facilities.
When solving the tasks of the second group, the expediency and possibility of joining productive formations is determined by analyzing the geological and commercial characteristics of the exploited and attached objects and changes in the indicators of operation of the attached formation [1, 3].
The addition of an oil or gas reservoir is allowed for joint operation if the following parameters approximately coincide:
a) permeability;
b) saturation of oil with gas;
c) contour positions;
d) properties of oil or gas;
e) the values of reservoir pressures brought to one mark.
In addition, the layers must be homogeneous in lithological composition and so that the static level of the attached horizon is not lower than the normal dynamic level of the exploited formation. Particular attention is paid to the waterlogging of the layers.
All these conditions determine the effective joint operation of objects in one well after joining.
When connecting layers using DC equipment, there is no need to comply with all of the above conditions, since optimal operating conditions are created by separating and regulating the operating mode of each of them. Therefore, the main technological parameters on which the efficiency of the attachment depends are the indicators of the development of the attached reservoir, and the changes that will occur in its hydrodynamics after the introduction of an additional independent production or injection well.
The influence of this well on the development parameters is determined by the corresponding hydrodynamic calculations. According to known methods, technological indicators of the development of the attached reservoir are calculated, which will take place after the attachment (the change in pressure in the reservoir in the drainage area, the flow rate of the "new" well and the corresponding changes in the flow rate of the surrounding wells, as a result of interference, are determined).
Thus, the assessment of the feasibility and possibility of joining productive horizons using equipment for dual completion is carried out in the following order [2].
The geological and commercial parameters of the exploited and attached horizons are analyzed, the nature of the operation of the layers after joining (joint or separate) is determined.
Technological indicators of the horizon development after its introduction are determined. These indicators are used to assess the feasibility of inclusion.
The technical condition of the well is being studied (the tightness of the column, the strength of the cement stone and the height of its lifting, the equipment of the wellhead, etc.), - the possibility of additional perforation and installation of the DC equipment is determined.
The efficiency of joining objects in a well is estimated by the amount of additional oil produced (taking into account the flow rate losses in the surrounding wells, as a result of interference) or the amount of additional water injected into the attached reservoir, which ultimately characterizes additional current production.
The overall effectiveness of the use of the DC method in the field as a whole when connecting layers is characterized by the number of wells transferred to dual completion, their total additional production obtained as a result of connecting layers.
The use of means of dual completion in order to solve technical problems of oil and gas production. The following tasks can be assigned to this task group:
a) implementation of downhole gas lift;
b) maintaining the reservoir temperature (heating) of the well products with the help of thermal waters to prevent paraffin deposition;
c) combining the functions of sampling and injection in one well;
d) the use of DC equipment for the purposes of separate research of jointly operated reservoirs and other tasks.
The expediency of using DC equipment to solve the tasks of the third group is determined by the need to improve the performance of wells and the availability of appropriate conditions.
In particular, when oil is extracted using a gas lift and if there is a productive gas reservoir at the field, the gas of the latter can be used for gas lift by lifting it to the surface. Regulation of gas supply to the fountain tubes is carried out with the help of the DC equipment.
The test of the downhole gas lift was successfully carried out in Turkmenistan at the Northern Goturdepe field.
Similarly, if there are thermal waters in the productive section with the help of DC equipment, the latter can be used to heat the production of the well and thereby prevent the loss of paraffin.
The possibility of using the DC equipment to solve the problems of the third group in some cases depends on the technical condition of the well.
For example, in order to avoid interplastic flows of liquid or gases behind the column, the latter must be sealed and must have a strong cement ring.
The effectiveness of the use of DC equipment to solve these problems is revealed as a result of comparing the technical and economic indicators of the operation of the well in the usual way with the indicators of operation with the DC equipment. In some cases, the economic efficiency is determined on the basis of additional oil production, because with the improvement of the fluid lifting technique, the current flow rate of the well can be significantly increased.
The tasks of the third group can be solved by transferring any number of wells to the DC, depending on the technical capabilities (the size of the well equipment, etc.) and the condition of the wells.
Each well for equipping under the DC is selected individually.
The considered groups of tasks, solved using methods of dual completion, have significant differences in importance in matters of increasing the efficiency of oil field development and their technological essence. Depending on this, the methods of technological expediency of application and economic efficiency for each group of tasks have certain features. In addition, the calculation methods have features depending on the stage of development of the field. Therefore, in this manual, the solution of development tasks through the method of dual completion is considered both at the design stage and during operation. At the design stage, the tasks of the first group are mainly solved, and only in some cases the second and third. In the process of operation, mainly the tasks of the second and third groups and much less often the first.
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