Oil Recovery in Clayey Pools
Research into Physical and Mineralogical Mechanism of Oil Recovery Decrease in Clayey Oil Pools
Tech Area / Field
- PHY-NGD/Fluid Mechanics and Gas Dynamics/Physics
- OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences
8 Project completed
Senior Project Manager
Lapidus O V
VNIIEF, Russia, N. Novgorod reg., Sarov
- Kazan State University / Scientific Research Institute of Mathematics and Mechanics, Russia, Tatarstan, Kazan
- TU Delft, The Netherlands, Delft\nUniversitat Leipzig / Fakultat fuer Physik und Geowissenschaften, Germany, Leipzig
Project summaryAs years-old practice shows, oil pool servicing with pumping poorly mineralized surface and service waters into an oil pool often causes drastic changes of its flow features and decreases oil recovery. There are standard cases, when layers of bulk clayeyness >3% practically cease to participate in the oil pool development. The studies show [Ref.1] that the swelling effect of clay cement of rocks doesn’t cause these negative phenomena. It has been shown basing on non-traditional approaches and special radiographic analysis methods that degradation of the filtration (flow) capability of resevoirs in such a case is of hydrodynamical rather than mineralogical and physical-and-chemical nature. Complex enough and depending on a number of factors (for example, availability of volcanic ash relicts) processes of secondary technogeneous transformations of the mineral skeleton caused by changes of hydrochemical conditions in a pool are implemented. Transformation of interstratified minerals, such as mica-montmorillonite, into proper montmorillonite with partially preserving separate fragments of the ferrous mica structure becomes the process of most importance. The process causes clay particle dispersion to form separate montmorillonite and mica blocks that are then carried away by a fluid flow. Contrary to a highly disperse montmorillonite that quickly coagulates in the smallest pores and deteriorates penetrability near pumping wells only, mica plates of size about 0.1×2.0 mm can move in a pool over long distances and are observed even in the product recovered. Having been fixed mechanically in inhomogeneities of pore channels, they create a reverse electroosmotic flow owing to non-compensated high electric charge on their surface that decelerates the flow process. Computations show that the effect is quite sufficient to cease the flow process almost completely for separate areas of an oil pool and form the so-called “electrokinetic shields” in a lithologically homogeneous reservoir that drastically decrease oil recovery in the pool.
It is practically impossible to withstand negative consequences of such phenomena using traditional technologies of affecting a pool. The purposefull development of special technologies requires the creation of a corresponding theoretical and methodological basis for detailed examination of causes and mechanisms of the above-mentioned processes and methods of neutralizing them.
The project goal is to develop a physical-and-mathematical model and numerical techniques to study hydrochemical processes and their influence on flow features of clayey oil pools.
The following principal tasks have to be solved to implement the project:
1. Development of systems of physical methods for analysis of properties and compositions of formations and sedimentary rocks (NMR-porosimetry, radiographic analysis), as applied to rocks in oil reservoirs mudded off.
2. Theoretical and experimental study and development of mathematical models of clayey mineral dispersion processes followed by migration of components in a pool, mechanical and electrokynetic blocking of the collector pores and appearance of a reverse electroosmotic flux.
3. Development of numerical techniques and codes to numerically simulate multiple-component flow in oil pools with taking account of physical and chemical processes causing changes of flow features of a pool.
4. Numerical studies of flow in clayey oil pools and selection of optimal methods to use the electroosmotic effect in new oil recovery technologies.
The methodology of implementing the project is based on the use of modern knowledge achieved when studying oil flow processes. Non-traditional methods, the corresponding equipment and computer systems for representing experimental data have been developed to perform experiments. To classify products of clayey mineral transformation from groups of micas and chlorites, in particular, the method of scanning the inverse space of textures developed at the department of mineralogy of the Kazan State University and at the laboratory of crystalography of the Orlean University (France) (see Refs.[2-5]) is used. The method is implemented using a special two-drive X-ray diffractometer with quasi-parallel geometry of the X-ray optical track. When theoretically studying the problem, great experience of the project participants in developing numerical models and code systems for simulations of two-phase flows with regard to different physical and chemical processes of subsurface hydraulic mechanics will be used (Refs.[6-9]).
The project team includes scientists and experts from Russian Federal Nuclear Center-VNIIEF and scientists from N.G.Chebotarev Research Institute for Mathematics and Mechanics of the Kazan State University.
The project may be further advanced in the following aspects:
– creation of code systems for real-time computer simulation of oil recovery in oil reservoirs mudded off.;
– studying possible methods to increase oil recovery in clayey oil reservoirs;
– development of physical monitoring methods to evaluate the efficiency of pool water interaction with materials resulted from man-made (technogeneous) affects on the pool.
The project meets ISTC goals in all aspects:
– it gives an opportunity VNIIEF scientists and technicians engaged in nuclear weapons development to re-orient their activity to civil purpose activities on the development of new oil recovery technologies;
– the project is based on recent scientific achievements in the area of simulation of hydrochemical flow processes and, thus, encourages integration of weapon scientists within the international scientific community;
– the project is of a certain commercial potential, because it promotes creation of the scientific and methodical foundation for further development of application code systems required for oil industry.
The project will result in the development of physical methods for studying properties and compositions of formations and sedimentary rocks in mudded-off reservoirs of oil pools, theoretical and experimental studies of clayey mineral dispersion processes with further migration of components in a pool, mechanical and electrokynetic blocking of the reservoir pores and occurance of a reverse electroosmotic flux. Numerical techniques and codes for numerically simulating multicomponent flow processes in oil pools with taking account of physical-and-chemical processes causing degradation of flow features of a pool will be developed and numerical studies to find optimal methods of blocking the reverse electroosmotic flux required for implementation in practice of new technologies for oil recovery from clayey pools will be performed.
Main results of the project will be published.