4.5. Displacement characteristics.
Characteristics of displacement are called functional dependence between the parameters of development. Displacement characteristics are divided into differential and integral.
Differential displacement characteristics describe the dependence of the current oil production rate or oil production rate on time. These characteristics are built up according to the field data. To build up the dependencies there are used the yearly or monthly parameters, built by well-known production data. Here are some of them:
(4.6)
Here q is the current oil production rate (per year, month), t - time (year, month) since the beginning of the development of an operation facility, q0 is the initial oil production rate. A, B are constants determined by the processing of the field data, typically using the least squares method.
Integral characteristics are the dependences between the accumulated recovery oil, water, liquids, water cut. Usually they are called in honor of the authors. Here are some of them:
Sazonov:
,
Kambarov:
,
Pirverdyan:
,
Nazarov-Sipatchyov:
,
Revenko:
,
Medvedskiy-Sevastyanov ALGOMES -1 for homogeneous reservoirs:
Medvedskiy-Sevastyanov ALGOMES -2 for complex reservoirs [14]:
Here Qн ,Qв , Qж – accumulative production rate of oil, water and liquid, Qp - drainage recoverable reserves, A,B, n, α,β – constants, defined by the method of least squares, q0 – initial level of oil production rate.
Differential displacement characteristics are used to assess and forecast the current indicators of development. Extrapolating the curves constructed according to the actual field data, we can predict the changes of indicators in the following time periods, if the processing development system is not changed, and there are no unplanned methods of stimulation. To evaluate the methods of flow stimulation we should compare the projected indicators without using methods of flow stimulation with the actual indicators after their application.
Integral displacement characteristics allow to assess the degree of development of the recoverable reserves and the effectiveness of the development system, to compare them with the project indicators. Extrapolating the built curves of the accumulated indicators, analyzing their changes in time at the existing development system. Comparing the extrapolated development indicators with the real indicators after application of methods of enhanced oil recovery (EOR), you can define additional oil production, that is, to assess the effect of the applied EOR.
It is necessary to notice the displacement characteristic, developed by Medvedskiy - Sevastiyanov, ALGOMES-2. Unlike the other characteristics it can be used for the complex structure reservoirs with two pool-reservoir systems, that is, for the models, discussed in paragraph 4.2. The peculiarities of its application and calculation method of the parameters are described in [14].
CHAPTER 5. OIL DEPOSITS DEVELOPMENT PROJECT DOCUMENTATION.
5.1. The problems of oil deposits development
Nowadays in Russia there are hundreds of oil deposits and fields that are in development. The largest deposits have already been developed. Modern prospect methods have allowed to reveal a lot of low-efficient fields with difficult-to-recover oil reserves. A number of oil-and-gas fields, oil-and-gas condensate fields, which have fractured-porous reservoirs, the formations, containing the high-viscosity oil have increased. Oil reserves in the structurally complex reservoirs are hard to recover.
For the development of the fields with difficult-to-recover reserves RITEK (Russian innovation fuel and energy company) [15] there is adopted the development system, that includes:
1). The integration of different oil layers (or horizons) in one production facility. The rational integration is the integration that does not decrease reservoirs oil recovery, that leads to the increasing of average daily production rate per well.
2). The adaptive system of the oil field development, consisting one or several production facilities.
This development system consists of one or more mutually agreed grids of production and injection wells with the dispersed and selective water flooding that allows to provide the industrial development and prospect works of oil reservoirs (development control, survey, clarification of geological structure of the formations).
3) The use of deep intense perforation of the formations with perforation channels length up to 50-100 cm.
4) The use of wells-trees with horizontal channels up to 100 mm in diameter, a length of 20 to 60 m, which allows to increase well productivity in 2-3 times.
The use of wells with the long horizontal borehole part of 500 meters and more.
5) Water flooding with a wide gas bank, selected from the gas deposits. Gas provides a high coefficient of oil displacement, water injection leads to high reservoir sweep flooding.
6) The use of formation blockers and additional production casing (4 inch) to close the developed highly water-saturated formations.