Oil Strata Research Articles

Heterogeneous geological conditions and differential enrichment of medium and high maturity continental shale oil in China

Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed. (1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally; continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity. (2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks; the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types. (3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable. (4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractures, and thin sandy layers, and then accumulate in laminae of argillaceous siltstone, siltstone, and argillaceous dolomite, and dolomitic siltstone suites, etc. with low organic matter abundance in the shale strata, resulting in differences in enrichment pattern.

Research on the Division of Small Layers of the Yan’an Group in the Western District of Mahuang Mountain

To supplement, adjust and improve the division plan of crude oil strata in the west of Mahuangshan Mountain. Combining well logging, core, and drilling analysis and testing data, Petrel software was utilized to classify and compare the 10 layers of the Yan’an Formation. Draw 6 “net-like” skeleton profiles for Ningdong No. 2 and No. 3 wells, involving 31 wells. On the basis of the large-layer strata division, Yan 8 and Yan 9 sections are divided and compared; five “net-like” skeleton profiles were drawn in the 5 well, involving 16 wells. On the basis of the large-layer division, the small-layer division and comparison were performed by Yan 8 and Yan 9. The results show that the Yan 8 oil layer is divided into two stratigraphic units, and Yan 8 and Yan 82, and the Yan 9 oil layer is divided into two stratigraphic units, Yan 91 and Yan 92; the Yan 2 layer in the 2 and 3 well blocks of Ningdong is in the marker layer. The top of the coal seam, Yan 8 layers in the Ningdong 5 well area is on the top of the auxiliary marker seam. The fine division of small layers into tiny layers of sedimentary microfacies, reservoir heterogeneity, development dynamic analysis, remaining oil distribution and other studies provide indispensable data.

Моделирование катагенетического преобразования силурийских нефтегазоматеринских толщ южного Предуралья, на основе статистической обработки результатов анализа Rock-eval

Моделирование катагенетического преобразования силурийских нефтегазоматеринских толщ южного Предуралья, на основе статистической обработки результатов анализа Rock-eval

Minimization of the negative influence on the biosphere in heavy oil extraction and ecologically clean technology for the injection of the steam with supercritical parameters in oil strata on the basis of new ecologically clean tubing pipes with heat-resistant coatings

Some ecological problems related to heavy-oil extraction and ways for minimizing the negative impacts of this process on the biosphere are discussed. The ecological hazard of, for example, frequently used multistage hydraulic fracturing of formation is noted and the advantages and perspectives of superheated steam injection are considered. Steam generators of a new type and ecologically clean and costeffective insulating for tubing pipes (TPs) are necessary to develop the superheated steam injection method. The article is devoted to solving one of the most important and urgent tasks, i.e., the development and usage of lightweight, nonflammable, environmentally safe, and cost-effective insulating materials. It is shown that, for tubing shielding operating at temperatures up to 420°C, the most effective thermal insulation is a highly porous material based on basalt fiber. The process of filtration deposition of short basalt fibers with a bunch of alumina thermal insulation tubing pipe coatings in the form of cylinders and cylindrical shells from liquid pulp is substantiated. Based on the thermophysical characteristics of basalt fibers and on the technological features of manufacturing highly porous coating insulation, the thickness of a tubing pipe is determined. During the prolonged pumping of the air at an operating temperature of 400°C in the model sample of tubing pipes with insulation and a protective layer, we find that the surface temperature of the thermal barrier coating does not exceed 60°C. Introducing the described technology will considerably reduce the negative impact of heavy-oil extraction on the biosphere.

A space-time Legendre spectral tau method for the two-sided space-time Caputo fractional diffusion-wave equation

The space-time fractional diffusion-wave equation (FDWE) is a generalization of classical diffusion and wave equations which is used in modeling practical phenomena of diffusion and wave in fluid flow, oil strata and others. This paper reports an accurate spectral tau method for solving the two-sided space and time Caputo FDWE with various types of nonhomogeneous boundary conditions. The proposed method is based on shifted Legendre tau (SLT) procedure in conjunction with the shifted Legendre operational matrices of Riemann-Liouville fractional integral, left-sided and right-sided fractional derivatives. We focus primarily on implementing this algorithm in both temporal and spatial discretizations. In addition, convergence analysis is provided theoretically for the Dirichlet boundary conditions, along with graphical analysis for several special cases using other conditions. These suggest that the Legendre Tau method converges exponentially provided that the data in the given FDWE are smooth. Finally, several numerical examples are given to demonstrate the high accuracy of the proposed method.

Use of Pulsed Neutron Reagent Control in Acoustic Action on Oil Strata

Use of Pulsed Neutron Reagent Control in Acoustic Action on Oil Strata

A New Method of Calculating Recovery of Waterflooding Reservoir by Using Production Rate

Development characteristics of oil field during production-decreasing stage were analyzed in this paper. The ultimate recovery factor can be determined at a limit of oil production rate by investigating the relationship between production rate and recovery percent. Some physical conditions were given. Based on the mass conservation principal and seepage mechanics method, it was found that the recovery degree varies versus production rate linearly. The model prediction using the actual data of west Ng63+4oil strata in Gudong 7 region, a reservoir in Shengli oilfield of China, was performed. The results demonstrated that the linear model had well estimation of the recoverable recovery of oil fields which were at the later period of high water cut stage.

Two finite difference schemes for time fractional diffusion-wave equation

Time fractional diffusion-wave equations are generalizations of classical diffusion and wave equations which are used in modeling practical phenomena of diffusion and wave in fluid flow, oil strata and others. In this paper we construct two finite difference schemes to solve a class of initial-boundary value time fractional diffusion-wave equations based on its equivalent partial integro-differential equations. Under the weak smoothness conditions, we prove that our two schemes are convergent with first-order accuracy in temporal direction and second-order accuracy in spatial direction. Numerical experiments are carried out to demonstrate the theoretical analysis.

Characterization of the aerobic hydrocarbon-oxidizing enrichments from a high-temperature petroleum reservoir by comparative analysis of DNA- and RNA-derived clone libraries

Enrichment cultures of aerobic hydrocarbon-oxidizing bacteria obtained from the injection and production wells of the Dagang oil field (China) were studied by molecular biological and microbiological methods. This work is the first to report simultaneous isolation of DNA and RNA from enrichment cultures of microorganisms from oil strata with further construction of clone libraries of 16S rRNA genes and 16S crDNA (complementary rDNA). Comparative analysis of the DNA- and RNA-derived clone libraries made it possible to determine the total genomic diversity of microorganisms, as well as to reveal metabolically active microorganisms in these cultures. Phylotypes of bacteria of the genus Geobacillus were found to be dominant in the DNA and RNA clone libraries of the enrichment cultures from the production well. Phylotypes of bacteria belonging to Geobacillus, Pseudomonas, Tepidiphilus, and other genera were detected in the DNA and RNA libraries obtained from the culture from the injection well. Phylotypes of bacteria of the genus Geobacillus were predominant in the RNA library and represented the second-largest group (after pseudomonads) in the DNA library. In the RNA libraries of the alkB genes of both enrichments, three homologs close to alkB-geo1, alkB-geo2, and alkB-geo4 of bacteria of the genus Geobacillus were detected. The occurrence pattern of the alkB transcripts, ribosomal RNA, and the 16S rRNA genes of bacteria of the genus Geobacillus indicates the predominance and functional activity of geobacilli in the enrichment cultures of hydrocarbon-oxidizing bacteria from high-temperature petroleum reservoir.

Numerical treatment of fractional heat equations

This paper is devoted to the numerical treatment of some fractional extensions of the temperature field problem in oil strata. Based on the Grünwald–Letnikov's definition of a fractional derivative, finite difference schemes for the approximation of the solution are discussed. By means of them the fractional heat equation is solved. The main properties of the explicit and implicit numerical methods developed, related to stability, convergence and error behaviour are also studied. Stability conditions as extensions of the CLF condition are derived and numerical experiments are provided.

Fractional extensions of some boundary value problems in oil strata

In the present paper, we solve three boundary value problems related to the temperature field in oil strata — the fractional extensions of the incomplete lumped formulation and lumped formulation in the linear case and the fractional generalization of the incomplete lumped formulation in the radial case. By using the Caputo differintegral operator and the Laplace transform, the solutions are obtained in integral forms where the integrand is expressed in terms of the convolution of some auxiliary functions of Wright function type. A generalization of the Laplace transform convolution theorem, known as Efros’ theorem is widely used.

Fractional extensions of the temperature field problems in oil strata

We consider fractional extensions of the incomplete lumped formulation and the lumped formulation of the temperature field problems in oil strata. Laplace transform is used to solve the corresponding heat equations with an additional term representing the internal heat sources. Efros theorem, a generalized form of the Laplace convolution, is used to obtain the analytic solutions. Special cases are mentioned.

Radio Isotope Method for Rapid Determination of Proppant Concentration in Working Mixtures Used in Hydraulic Fracturing of Oil and Gas Containing Strata

A radio isotope method for rapid determination of proppant concentration and a test measurement unit RIKP-01 constructed on the basis of it provides a relative error in determining proppant concentration of not more than ± 3.5% with a measurement time of 15 sec that is four times better than for the world leader, i.e., the firm Halliburton (USA).

On the Lauwerier formulation of the temperature field problem in oil strata

The paper is concerned with the fractional extension of the Lauwerier formulation of the problem related to the temperature field description in a porous medium (sandstone) saturated with oil (strata). The boundary value problem for the fractional heat equation is solved by means of the Caputo differintegration operator of order 0 < α ≤ 1 and the Laplace transform. The solution is obtained in an integral form, where the integrand is expressed in terms of a convolution of two special functions of Wright type.

Use of Microorganisms in the Biotechnology for the Enhancement of Oil Recovery

The existing methods of oil field exploitation give the opportunity to extract no more than half of the geological resources of oil; from carbonate oil collectors, only 20% of oil is extracted [1]. Furthermore, the portion of recovered oil is tending to decrease due to the development of deposits of viscous oils under difficult geological and physical conditions. Thus, new methods for enhancing oil recovery are needed to at least maintain oil extraction at a constant level. There are various chemical and physicochemical methods for enhancing oil recovery. The method of secondary flooding, developed by the Soviet academician A.P. Krylov in the 1930s, is widely used in many oilproducing countries. Surface water is pumped into the oil stratum through a system of water-injection wells, which results in an increase in the stratal pressure. This technology is highly efficient. Chemical methods, used in combination with secondary flooding, belong to the so-called tertiary methods of oil recovery enhancement. These include immiscible flooding (alkaline or polymeric) and miscible flooding with solvents and acids, as well as flooding with the use of surface-active compounds (surfactant flooding, or microemulsion flooding). The surfactants widely used in Europe and North America are chemically synthesized oil sulfonates. Gas injection is also applied, with CO 2 , N 2 , and hydrocarbon gases being mainly used. Thermal methods include injection of a heat carrier (hot water or vapor) or intrastratal combustion. Selective plugging of highly permeable layers for the improvement of flooding is little used in Europe and Siberia but is widely applied in North America, Canada in particular [2]. The development of methods for microbial enhancement of oil recovery started in the middle of the 20th century. They are highly efficient and diverse, environmentally safe, and relatively cheap, although science-intensive. Three substantial prerequisites exist that allow us to believe in the prospects for the development of new efficient biotechnologies for enhancing oil recovery based on the geochemical activity of microorganisms. First, oil fields exploited with water flooding are widely inhabited by aerobic and anaerobic microorganisms belonging to various physiological groups, which retain viability and biochemical activity in oil strata. Second, microorganisms are able to degrade oil hydrocarbons to smaller and more labile organic molecules and to synthesize such oil-releasing agents as ee 2 , ec 4 , fatty acids, alcohols, polysaccharides, surfactants, and other technologically active substances. Third, microorganisms are capable of in situ production of oil-releasing substances directly in zones and microzones containing residual oil. Present research that aims at the development of biotechnologies for oil recovery enhancement should be concerned with study of the regularities of microbial distribution and geochemical activity in oil fields under different geophysical conditions, as well as with advanced investigation of physiological and biochemical characteristics of microorganisms and development of methods for regulation of microbial processes in oil fields [3].

Simulating Cold Heavy Oil Production With Sand by Reservoir-Wormhole Model

Abstract Continuous sand production and foamy oil behaviour are both believed to be key factors for the enhanced non-thermal fluid production in unconsolidated heavy oil reservoirs in Canada (Alberta and Saskatchewan). The same mechanisms are plausible to be active in similar heavy oil strata in Venezuela (Faja del Orinoco), Oman, and China. Field experience indicates that a fundamental understanding of sand production mechanisms, foamy oil behaviour, pressure gradient changes, and stress changes are essential to successful operations involving massive continuous sanding. Inter-relating these factors requires the coupling of geomechanics and fluid flow processes. An integrated approach incorporating a three-phase, threedimensional, black-oil model coupled with a geomechanics model is introduced in this article. Piping channels (wormholes) are postulated to develop from perforations when pressure gradients exceed the residual cohesion of the sand formations. An elastoplastic constitutive model is extended to describe the reservoir material before seepage forces liquefy and suspend the sand particles at the advancing tips of wormholes. The hemispherical wormhole tip is postulated to propagate as long as a critical tipressure gradient is exceeded. A slurry transport model is usedo describe the flow inside the wormholes. Field data from Frog ake, Alberta are used to validate the model, and it appears that the simulation and the field data are well-matched. Introduction An operational strategy of producing heavy oil with sand has been widely used for a decade in Alberta and Saskatchewan(1–6). However, a poor understanding of this production process, a recovery rate limited to ˜12 - 20% in appropriately screened reservoirs, and difficulties in well management (i.e., repeated workovers) have been the weak points for this technology(7). Improving these aspects, particularly the understanding of this enhanced production mechanisms, can be vital to achieving direct economic benefits. This article introduces a model to address reservoir fluid mobility changes arising from sanding, and pressure drive changes arising from foamy-oil flow. Simulations are based on a general three-dimensional, four-phase, black-oil production model coupled with a slurry flow model (i.e., solid phase is the fourth phase simulated). The latter model represents the wormholes network (or slurry transport zone), and the material balance for solids transport is established. Alternatively, the volumetric sand production and enhanced oil production have also been calculated by a coupled geomechanics model(7–9), in which fluid flow is simultaneously solved with a solid deformation system. Sand production and enhanced oil production contribute to the development of a continuous sanding zone adjacent to the wellbore. In an attempt to simulate cold heavy-oil reservoir production (CP) in Northwestern Canada, where some evidence indicates that large-scale wormholes or high-permeability channels exist inside the reservoir formations(3), a wormhole model is proposed. The proposed model is developed based on the hypothesis that the reservoir formation is poorly consolidated, thus wormhole development under a critical flow velocity or pressure gradient is possible. A detailed discussion on the wormhole model can also be found elsewhere(10). Background Sand production has long been considered undesirable(11, 12), but it is associated with high drawdown and production rates, which are required for faster and more profitable oil production.

Some boundary value problems of temperature fields in oil strata

We consider two boundary value problems related to the temperature fields in oil strata. Laplace and a generalized Hankel transform are used to obtain the desired solutions. Efro’s theorem, which is a modified form of the convolution theorem for the Laplace transform is generalized using confluent hypergeometric function. Particular cases of our results established here are in agreement with some known results given in the literature.

Numerical methods for determining filtration parameters for inhomogeneous oil strata

We describe a number of nonlocal hydrodynamic methods for determining filtration parameters for inhomogeneous oil strata and flow models. Numerical algorithms based on projection-difference, integral, finitedifference, and regularization methods are used to solve these problems. Numerical computations based on the algorithms are presented.

Mathematical simulation of biogenic processes in oil strata

An attempt is made to construct a mathematical model of the development of bacteria in an oil stratum and investigate on the basis of this model the main features of the process.

Micellar-polymer flooding of oil strata under conditions of irreversible sorption

Micellar-polymer flooding of oil strata under conditions of irreversible sorption