Exploration Of Oil Fields Research Articles

SOME LIMITATIONS OF ENHANCED OIL RECOVERY IN INDONESIA

Enhanced Oil Recovery (EOR) technologies are now being developed year by year. Some of technologies are already applied in pilot or commercial scale in actual oilfields. Meanwhile, conditions for the exploration of new oil fields are becoming more severe. Accordingly the qualification as being an operator in many oil companies is going to be justified in terms of their capability in EOR technology in addition to the capability of exploring new oil fields.

Identification of low-resistivity-low-contrast pay zones in the feature space with a multi-layer perceptron based on conventional well log data

In the early exploration of many oilfields, low-resistivity-low-contrast (LRLC) pay zones are easily overlooked due to the resistivity similarity to the water zones. Existing identification methods are model-driven and cannot yield satisfactory results when the causes of LRLC pay zones are complicated. In this study, after analyzing a large number of core samples, main causes of LRLC pay zones in the study area are discerned, which include complex distribution of formation water salinity, high irreducible water saturation due to micropores, and high shale volume. Moreover, different oil testing layers may have different causes of LRLC pay zones. As a result, in addition to the well log data of oil testing layers, well log data of adjacent shale layers are also added to the original dataset as reference data. The density-based spatial clustering algorithm with noise (DBSCAN) is used to cluster the original dataset into 49 clusters. A new dataset is ultimately projected into a feature space with 49 dimensions. The new dataset and oil testing results are respectively treated as input and output to train the multi-layer perceptron (MLP). A total of 3192 samples are used for stratified 8-fold cross-validation, and the accuracy of the MLP is found to be 85.53%.

Methodological approaches to additional exploration of oil fields

Methodological approaches to additional exploration of oil fields

Identification of CO2 using multiple formation properties based on nuclear logging

The use of carbon dioxide to enhance oil and gas recovery (CO2-EOR) plays an important role in carbon capture, utilization, and storage (CCUS). CO2 monitoring is of great significance for understanding CO2 migration mechanisms, leakage pathways, and storage effect, and it is help for optimizing the performance of CO2-EOR and risk assessment. Moreover, oil and gas fields involving CO2 also need to monitor and identify CO2 layers to support decisions on oil and gas exploration and development. The purpose of this study is to use nuclear logging methods to distinguish CO2 from other fluids, including hydrocarbon gases, and to monitor and identify CO2. Based on the differences in the formation properties of CO2 and other fluids, a slope method is proposed. The slopes related to different formation properties are calculated by the Monte Carlo method. The sensitivity of various slopes in distinguishing CO2 from hydrocarbon gases (hereinafter referred to as “sensitivity”) is analyzed. The cross-plot of slopes with high sensitivity is used to identify CO2 from other fluids. The effects of various environmental factors on the cross-plot and the applicability of the cross-plot method are analyzed. The results indicate that the positions of CO2 points in the cross-plot are greatly different from the positions of water, oil, and CH4, and the cross-plot can effectively identify CO2 from other fluids. Lithology and shale content have little effect on the performance of the cross-plot in identifying CO2 from other fluids. Comparatively, gas density and water saturation have greater impacts on such performance. The results of interpretation of field data obtained with the new method are basically consistent with the sample results, indicating that the new method is effective. This method can provide strong support for making decision on the exploration and development of oil and gas fields and has promising prospects for application in CO2 monitoring in CO2-EOR.

Determination of geomechanical properties of the Jurassic and Pre-Jurassic sediments of the Tomsk region

Introduction. Geomechanical properties of rocks are used as input data for geomechanical modeling and subsequent calculations of hydraulic fracturing design, assessment of sand production of wells, calculation of drilling stability, assessment of fracturing, and other exploration and development of oil and gas fields related to geomechanics. The quality of the calculations performed significantly depends on the accuracy of determining the geomechanical properties of rocks. However, their accurate determination requires a large volume of core studies, which are often absent. This paper summarizes the correlation between geophysical parameters and geomechanical properties for a series of fields in the Tomsk region, located in the southern part of the Nyurolskaya depression. The above correlations can be used in other fields with similar geological conditions, where the research volume is low or laboratory research is absent. Research objective. Generalization of correlations in the form of diagrams between geophysical parameters and geomechanical properties (Young’s modulus, Poisson’s ratio, ultimate strength, and tangent of the angle of internal friction) for a series of fields in the Tomsk region located in the southern part of the Nyurolskaya depression. Methods of research. The proposed schemes are based on laboratory studies of core samples of various lithotypes, as well as statistical analysis of the data obtained. Research results. The result of the work is the scheme for calculating the mechanical properties. According to the proposed schemes, first, the lithology of the described rocks is considered; then, based on the available set of geophysical studies, a correlation dependence with the specified uncertainty interval is selected. Conclusion. The results of the work conducted make it possible to carry out geomechanical modeling in the shortage or absence of laboratory core studies for the field studied. It is recommended to clarify the proposed correlations when conducting laboratory studies for the object under study.

Analysis of wellbore stability of gas underbalanced drilling technology

Gas underbalanced drilling technology has the advantages of high ROP and little damage to oil and gas reservoirs. In recent years, it has been widely used in the exploration and development of oil and gas fields in China. Under normal air drilling conditions, the pore pressure is basically zero, so it is necessary to establish the wellbore stability model under the condition of zero pore pressure to provide theoretical support for the wellbore stability analysis of air drilling. However, gas underbalanced drilling also has wellbore instability, more sand deposition at the bottom of the well, and even the malignant accident of sticking. Firstly, through the analysis of the traditional wellbore stability model, the influence of pore pressure is removed, and the wellbore stability model suitable for air drilling is obtained. At the same time, it is proposed that the sand deposition is mainly caused by the collapse material when the collapse ellipse is formed on the shaft wall, and the formation of the collapse ellipse is conducive to maintaining the stability of the shaft wall. For large and medium-sized gravel layers, the influence of cementation strength on wellbore stability should be considered.

Study on feasibility and mechanism of the subcritical oxidation of waste drilling mud

Waste drilling mud (WDM) is a hazardous and refractory waste generated during the exploration of oil and gas fields. WDM has high chemical oxygen demand (COD) and high salinity, making it difficult to handle WDM. In this study, WDM was treated under subcritical conditions without and with hydrogen peroxide (H2O2) or potassium persulfate (K2S2O8). The removal efficiency of CODCr (COD was measured by potassium dichromate method) reached 98.20% ~.99.6%. The contents of twelve heavy metals in liquid products were lower than the emission limit except for arsenic. But arsenic concentration decreased by 65.25%. Those detected heavy metals were almost completely removed into solid products. In addition, after introducing K2S2O8 as an oxidant, the removal efficiency of total organic carbon (TOC) in the liquid increased by 58.34% and 13.43% compared with additive-free and H2O2, respectively. The removal efficiency of total nitrogen (TN) was the same as above, also increased by 70% and 59.26%, respectively. The results showed that the introduction of K2S2O8 was more effective in treating WDM under subcritical conditions. Moreover, the introduction of K2S2O8 can generate sulfate ions. Sulfate ions can form stable metal salts with lead and barium, which was conducive to the immobilization of heavy metals. This study provides a new way for the harmless treatment of WDM, and also further expands the application scope of subcritical oxidation.

Semi-Supervised Learning–Based Petrophysical Facies Division and “Sweet Spot” Identification of Low-Permeability Sandstone Reservoir

The identification of the “sweet spot” of low-permeability sandstone reservoirs is a basic research topic in the exploration and development of oil and gas fields. Lithology identification, reservoir classification based on the pore structure and physical properties, and petrophysical facies classification are common methods for low-permeability reservoir classification, but their classification effect needs to be improved. The low-permeability reservoir is characterized by low rock physical properties, small porosity and permeability distribution range, and strong heterogeneity between layers. The seepage capacity and productivity of the reservoir vary considerably. Moreover, the logging response characteristics and resistivity value are similar for low-permeability reservoirs. In addition to physical properties and oil bearing, they are also affected by factors such as complex lithology, pore structure, and other factors, making it difficult for division of reservoir petrophysical facies and “sweet spot” identification. In this study, the logging values between low-porosity and -permeability reservoirs in the Paleozoic Es3 reservoir in the M field of the Bohai Sea, and between natural gamma rays and triple porosity reservoirs are similar. Resistivity is strongly influenced by physical properties, oil content, pore structure, and clay content, and the productivity difference is obvious. In order to improve the identification accuracy of “sweet spot,” a semi-supervised learning model for petrophysical facies division is proposed. The influence of lithology and physical properties on resistivity was removed by using an artificial neural network to predict resistivity R0 saturated with pure water. Based on the logging data, the automatic clustering MRGC algorithm was used to optimize the sensitive parameters and divide the logging facies to establish the unsupervised clustering model. Then using the divided results of mercury injection data, core cast thin layers, and logging faces, the characteristics of diagenetic types, pore structure, and logging response were integrated to identify rock petrophysical facies and establish a supervised identification model. A semi-supervised learning model based on the combination of “unsupervised supervised” was extended to the whole region training prediction for “sweet spot” identification, and the prediction results of the model were in good agreement with the actual results.

Research and application of water flooding injection and production technology after polymer flooding

For reservoir water flooding after polymer flooding injection points existing in the mining process of high temperature resistant performance is poor and multistage unlock difficulty, examination, and the sealing problems such as in-depth study and analysis, innovation to a new set of return to spit points injection points production technology, to produce more suitable sealing high voltage can be found on a variety of well conditions return to spit points a column technology, is helpful for better improvement points injection tube service life, At the same time, it can effectively solve the problem of clogging downhole concentric test and adjustment unit. Oilfield exploration into the follow-up after water flooding stage, the well will show the water fast, fast production decline, the characteristics of a return so often need to take back to spit on mining technology, but the technology has high pressure resistance and multistage unlock difficulty problem, makes the life of the mining process is shorter, so according to the technical problems existing in the in-depth study and analysis, The effective outcome measures are put forward to provide necessary technical support for reservoir benefit after polymer flooding.

Discussion on the influence of geological parameters on reservoir development in Daqing Oilfield

With the improvement of social development level, the development speed of all walks of life has been rapidly improved. This increase in speed makes the industry’s demand for energy also show a growing trend. Based on this, relevant departments have also increased the research on oilfield exploration and reservoir development. Among them, through research, it is found that geological parameters have a very significant impact on the oil reservoir development effect. Only based on geological parameters can the developed oil reservoir have the support of objective data and guarantee the development effect. This paper will analyze and study the influence of geological parameters on reservoir development in Daqing oilfield.

ОПТИМИЗАЦИЯ ИНВЕСТИЦИОННЫХ ПРОЦЕССОВ РАЗВИТИЯ НЕФТЯНОЙ ОТРАСЛИ

The article develops a methodology of determining the optimal indicators of the investment program for the development of the region oil industry. The issues of assessing the effectiveness of capital investments in the exploration and development of oil fields, taking into account the delayed and distributed over time impact of such investments on the volume of crude oil production, were investigated. The methodological basis of the study is mathematical modeling of investment processes in the oil industry using distributed lag models. Much attention is paid to the study of the influence of random factors on the effectiveness of capital investments and the parameters of the optimal investment program. The article develops a methodology that allows excluding the vector of unobservable system parameters from the equations of the mathematical model and takes into account the change in the nature of the influence of random factors when replacing endogenous parameters of the model. The proposed model of the investment process shows how the efficiency of capital investments in the development of the region oil industry increases depending on the accepted structure of such investments lag. The conclusion indicates the possibilities for improving the efficiency of investments using the developed model. The authors propose to synthesize the global optimization method with the included distributed lag model, which is used according to the method improved in the article.

Elastic impedance inversion method based on Quantum Annealing MH algorithm

Seismic inversion is one of the important methods to realize reservoir prediction in oil and gas field exploration. The seismic stochastic inversion based on Metropolis-Hastings algorithm makes full use of well logging data and improves the vertical resolution of inversion results. However, conventional Metropolis-Hastings algorithm has slow convergence speed and poor stability. In this paper, an elastic impedance inversion method based on optimized Metropolis-Hastings algorithm is established by combining quantum annealing algorithm with Metropolis-Hastings algorithm. The feasibility of the method is verified by model calculation and actual data test.

Characterization of magnesium oxide nanoparticle for water-based drilling mud formulation

This research is based on the synthesis and analysis to determine the efficiency and cost effectiveness of nanoparticle materials used in drilling fluid during oilfield exploration process. The study was carried out in the formulation of a waterbased drilling fluid, in which the prepared additives were treated with magnesium oxide (MgO) nanoparticles. The rheological properties of nanoparticle materials, such as flow time, viscosity, shear rate, shear stress, torque difference, and separation of solids and liquids, have been determined. The study also analyzed the fluid loss with respect to time in a manual filter press for low temperature and low pressure versus high pressure and high temperature using filter press hydraulic dead weight assembly in high temperature and high pressure. The nanoparticle used for the study was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer and particle size analyzer. Viscosity parameters were optimized using a multi-speed viscometer, lubricity tester and pH meter at effective concentration, as well as contact time, temperature and pressure changes as a function of concentration. The study suggests the use of MgO nanoparticle as an additive for water-based mud exploration in oilfields.

Estimating Reservoir Properties from 3D Seismic Attributes Using Simultaneous Prestack Inversion: A Case Study of Lufeng Oil Field, South China Sea

Summary Lufeng oil field was discovered in the 1980s in the Pearl River Mouth Basin (PRMB) of the South China Sea and has entered the stage of secondary oil recovery. One major problem that has restricted the subsequent exploration of the oil field is the unclear regional reservoir and caprock distribution, because practitioners have been using post-stack attributes and acoustic impedance inversion to analyze the distribution of sandstone (reservoir) and mudstone (caprock). In current geophysical research on reservoirs and caprocks, prestack inversion has been widely used because of its advantage over post-stack inversion. However, the accuracy of using single P/S-wave velocity ratio (VP/VS) or density (Vden) inverted by prestack to predict lithology is still insufficient. In this study, we created a new attribute VRDEN, the sum of VP/VS and the weighted Vden, to capture the lithology variation of the reservoir. We integrated 3D seismic data and well log data and applied simultaneous prestack inversion and multiattribute regression analysis to determine reservoir properties, such as sand thickness, effective porosity, and distribution of sandstone and mudstone of the Lufeng oil field. Then, we calculated the new attribute VRDEN from VP/VS and Vden obtained from simultaneous prestack inversion to determine the lithology variation. The multiattribute regression analysis, combining prestack attributes and post-stack attributes, indicates the effective porosity and sand volume in the Enping Formation, which contains the main oil-bearing reservoirs in the Lufeng oil field. Results show that when the sandstone thickness is greater than 12.5 m, the prediction error of VRDEN is the lowest compared with VP/VS and Vden. In En-2 member of the Lower Enping Formation, medium- to high-porosity (14 to 17%) sandstone (19.5 m thickness) is widely distributed in the west and middle of the study area, with an area of nearly 300 km2. The high-porosity sand zones stretch from the east of the Lower Enping Formation to the west of the Upper Enping Formation, which is the result of westward progradation of the braided delta. Our workflow used a novel seismic attribute VRDEN in the simultaneous prestack inversion and multiattribute regression process to provide a more predictive spatial distribution of reservoir-nonreservoir features. The improved reservoir understanding will allow more efficient exploitation of the Lufeng oil field, and the improved workflow will facilitate exploration of other oil fields in the world.

FLUID DYNAMIC ANALYSIS OF A MARINE SOIL IN JETTING EXCAVATION EMPLOYING RHEOLOGICAL MODELS: INFLUENCE OF DRILLING FLUID ON SOIL DEFORMATION

With the exploration of marine oil fields in deep and ultra-deepwater regions, the need for studying different methods of well construction has increased. Nowadays, the technique of laying conductive casing by jetting is the most widely used for the starting phase of a well in such conditions. In this scenario, in early layers, where the marine soil is in contact with seawater, this material can present itself as a fine mud, characterizing a cohesive non-drained soil, with low shear strength, being considered a material with viscoplastic behavior. Thus, as such, using fluid rheology to analyze it may represent a valid option; being possible to classify it as a Herschel-Bulkley fluid. The use of computational modeling and numerical simulation represent an alternative to understand the behavior of soil during jetting. In this context, this work focuses on developing a computational modeling of the jetting of marine soil, based on the soil fluid dynamics approach, using computational fluid dynamics (CFD - Computational Fluid Dynamics) software SIMULIA XFLOW, version 2020. This work aims to investigate the deformation in the seabed in response to an incident vertical jet using different drilling fluids, also modeled as viscoplastic materials. Drilling fluids suitable for jetting and a fluid with a higher specific mass were considered. For the proposed modeling of the soil and drilling fluids considered, the main parameters used were the yield point, consistency index, behavior index, and the boundary viscosity. The latter was necessary to implement the modified Herschel-Bulkley model used by the software. Results show that the excavated cavity presented a similar behavior for the drilling fluids suitable for jetting, indicating that the rheology of the drilling fluid does not interfere with the deformation of the soil. However, a significant influence on the profile of the excavated cavity was observed when implementing the drilling fluid of higher specific mass in the jetting, which deformed the soil at greater depths.

Study on characteristics of tight oil reservoir in Ansai Area of Ordos Basin– take the Chang 6 section of Ordos Basin as an example

ABSTRACT In order to understand the exploration and development potential of tight oil in the oil field exploration and development stage, the reservoir characteristics of Chang 6 oil formation in Ansai area of Ordos Basin were studied. In this paper, the reservoir characteristics are studied by using aseries of experimental data, such as cast sheet, cathodoluminescence, electron probe, conventional mercury injection, constant rate mercury injection experiment, scanning electron microscope, etc. The results show that the lithologic characteristics of Chang 6 reservoir group in Ansai area are mainly feldspathic sandstone, accounting for 64.57%, followed by lithic feldspathic sandstone accounting for 31.36%, the sum of the two accounting for 95.93%. Pores are most developed in Ansai area, and the interstitial materials are mainly chlorite, kaolinite and illite. Primary intergranular pores are mainly developed in this area. Besides primary intergranular pores, there are also some feldspar dissolved pores in Ansai region. There are many laumontite dissolved pores in this region. The reservoir type in Ansai region is “low porosity and ultra low permeability”, but the Chang 6 member reservoir in Ansai region is very well characterized by “low porosity and ultra low permeability”.

Polymers for enhanced oil recovery: fundamentals and selection criteria revisited.

As the energy demand is escalating tremendously and crude oil being the primary energy source for at least the next two decades, the production of crude oil should be enhanced to meet the global energy needs. This can be achieved by either exploration of new oil fields for crude oil extraction or employing enhanced oil recovery (EOR) technology to recover the residual oil from existing marginal oil fields. The former method requires more capital investment and time; therefore, this review focuses on the latter. In general, the abandoned oil fields still have 50% of crude left which is unrecovered due to lack of technology. Hence, EOR came into existence after the conventional methods of recovery (primary and secondary recovery) were found to be inefficient and less economical. Nineteen percent of the EOR projects are based upon cEOR methods worldwide, of which more than 80% of projects use economically feasible polymer flooding process for oil recovery. Both synthetic and naturally derived polymers have been used widely for this purpose; however, many recent studies have shown the lower stability of synthetic polymers under extreme reservoir conditions of high salinity and temperature. Additionally, naturally derived polymers face microbial degradation as the major limitation. Therefore, a number of novel polymers are currently studied for their suitability as an efficient EOR polymer. Latest findings have also revealed that biopolymers play an important role in wettability alteration, pore evolution by bioplugging, and reducing fingering effect. Injection of biopolymers can also lead to the selective plugging of thief zones which redirects water flood to the inaccessible oil pores. Therefore, the current study focuses on such principle and mechanism of polymer flooding along with the reservoir and field characteristics which affects the polymer flooding. It also discusses the scope of biopolymer along with the screening criteria for use of novel polymers and strategies to overcome the problems during polymer flooding. KEY POINTS: • Discussion of macroscopic and microscopic mechanisms of polymer flooding. • Screening criteria of polymers prior to flooding are essential. • Biopolymers are eco-friendly and are applicable for a wide range of reservoir conditions.

Research and application for the non-landing treatment technology of water-based drilling solid-liquid waste in Northwest China

Water-based drilling solid-liquid waste is the most common environmental pollutant in the process of oil and gas exploration and development. Due to leakage or untreated discharge, these drilling solid-liquid wastes enter the atmosphere, water bodies, and soil, and cause serious pollution to the surrounding ecological environment. At present, how to reduce the heavy metals and other toxic and harmful components in water-based drilling solid-liquid waste, make it meet the discharge standards or recycle it is a major problem that plagues the sustainable development of oil and gas fields. This article introduces the sources and characteristics of water-based drilling solid-liquid waste, summarizes the domestic research status of solid-liquid waste treatment technology for foreign water-based drilling, analyzes the characteristics and advantages of drilling waste non-landing technology treatment. It is pointed out that it is necessary to adopt drilling water-based solid-liquid waste non-ground treatment technology in the exploration and development process of oil and gas fields in Northwest China, and it has good application prospects.

Drilling Supporting Technology for Exploration and Development of A Marginal Oilfield

Marginal oil fields refer to some small and medium-sized oil fields or oil fields with complex stratigraphic structure and located in remote areas. There are more than 100 large and small blocks marginal oil fields with huge reserves. They have the characteristics of geological reservoirs such as structural fracture, fault development and complex oil reservoirs. The development is uncertain and is not suitable for excessive investment. How to carry out economic and effective exploration and development of marginal oil fields has become a new breakthrough in stabilizing production and improving benefits in A oilfield, as the first marginal oil field with “extended test of development evaluation wells + overall development plan”, designed and manufactured three hole asymmetric underwater wellhead base plate in combination with mudline hanger in order to meet the needs of overall oilfield development, Realize the temporary abandonment of the extended test well after the test, and put it back into production in the overall development stage of the oilfield. It provides a new mode of cost reduction and efficiency increase for the subsequent development of marginal oil fields, which will revitalize a large number of marginal oil fields to be developed and bring huge economic and social benefits. The establishment of a safe risk response mode of “advance can be attacked and retreat can be defended” can improve the efficiency of preliminary research and avoid the risk of oilfield development.

Application of a geostatistical algorithm for correcting well logging data when modelling complex hydrocarbon deposits at the stage of additional field exploration

Background. Additional exploration of oil and gas reserves requires the application of information technologies for modelling all technological processes and interpreting the results of geophysical well logging. Reliable models of the object under exploration and the use of best practices in the field of information systems reduce investment risks associated with planning exploration works, at the same time as optimizing the planning and design of the entire process of field development.Aim. Optimization of the selection process of multivolume, multiparameter logging data when modelling a complex oil reservoir at the stage of additional field exploration, grouping well data by quality, completeness and uniformity of their distribution over the study area, as well as identifying inaccuracies (errors) in the field data (registration of signals in probes, errors in measurements of directional survey, borehole picks, etc.).Materials and methods. Examples of well logging interpretation for a complex reservoir are given, along with its distribution options for a constructed lithology cube (2D, 3D) based on the data obtained during drilling from one pilot borehole – a horizontal well, a sidetrack and a directional well. It was established that the data obtained when distributing the reservoir and modelling the lithology cube of a complex development target can be significantly different for wells located close to each other. The results obtained when constructing 2D and 3D models by different specialists revealed discrepancies in the interpretation and cross-well correlation of well sections.Results. Local zones with a sharp change in the structure were established, in particular, the concentration of extrema around some wells. The presence of such anomalies points to the presence of wells, for which the values of stratigraphic depth marks for wells located close to each other are quite different. A geostatistical algorithm was applied to correct the well data using the “sliding window” method, which became a solution for the most accurate determination of the depths of the object under exploration.Conclusions. The possibility of using a geostatistical algorithm for correcting well data based on multiparameter geophysical data was assessed; the current state of modelling the processes of exploration and development of oil fields with a complex geological structure was analysed.