Oil-gas Field Research Articles

Mesozoic–Cenozoic tectonic controls on the formation of large‐scale metamorphic rock buried‐hill reservoirs in Bozhong Sag, eastern China

Buried‐hill reservoirs are important targets for petroleum exploration. The number of buried‐hill oil–gas fields with reservoirs hosted in metamorphic rock is low, and metamorphic rock buried‐hill reservoirs deeper than 4,500 m (ultra‐deep) are even rarer. Ultra‐deep metamorphic rock buried‐hill reservoirs are characterized by highly heterogeneous lithologies and structure and have complex formation mechanisms, but such reservoirs have received relatively little research attention compared with reservoirs hosted in other rock types and at shallower depths. In the Bozhong Sag in the Bohai Bay Basin, Archean metamorphic rocks are buried at depths of 4,500–6,000 m, and their anticlinal structures are thus defined as ultra‐deep buried hills. Owing to their burial depth and compacted overburden, tectonism has been a key control on the formation of high‐quality reservoirs by causing deformation such as fractures. In this study, using results of drill‐core analyses, thin‐section imaging, and rock mechanical tests, we investigated the distribution and formation mechanisms of high‐quality reservoirs within the Bozhong 19‐A metamorphic rock buried hill. We also examined the formation mechanism of fractures in the Bozhong 19‐A buried hill with respect to early‐stage initiation by compression and late‐stage reactivation by transpression. Results show that intense compression‐related overthrusting caused by collision between the South China and North China plates during the Indosinian (252–237 Ma) orogeny generated initial fractures in the metamorphic rock buried hill and the formation of numerous NW‐trending nappe structures. Subsequent Yanshanian (163–66 Ma) sinistral transpression not only reactivated pre‐existing fractures, but also resulted in the development of numerous new fractures. In addition, in low‐stress regions such as anticline flanks and the lower parts of structures, compression closed the pre‐existing fractures, leading to lower fracture densities. Results of acoustic emission mechanical testing indicate that Himalayan (66–0 Ma) extensional stress was insufficient to produce large‐scale fracture systems in the Archean metamorphic rock, but was crucial for reactivating pre‐existing early‐stage fractures. Thus, the Himalayan period was a key interval for the formation of effective fractures. Therefore, rocks that underwent large‐scale overthrusting during early‐stage (Indosinian) fracturing and subsequent late‐stage (Yanshanian and Himalayan) reactivation favoured the development of ultra‐deep metamorphic rock buried‐hill reservoirs. This study should provide guidance for petroleum exploration in buried hills in superimposed basins that underwent early‐stage compression, late‐stage transpression, and final extension.

Effect estimation of variations of petrophysical and lithological-facial characteristics on the quality of reservoir rocks

The paper presents the results of researches on the specification of clay components, as well as the zones of intra- and interstratal fluid flows in the formation processes of oil-gas fields. The investigations have been carried out in the context of Sangachal-Duvanny-Khara-Zira (SDKhZ) field, located in Baku archipelago of South Caspian basin (SCB). It was defined that the presence of clayey chlidolite in the reservoirs are observed more effective in the values of permeability rates. The zones of intra- and interstrata of fluid flows in the reservoirs were specified based on the lithological model of productive horizons. Therefore, the presence of closed migration-flow (drainage) system both within productive horizons and in the scale of reviewed field was supposed. In support of these assumptions, 2D and 3D variation models of flow zones indicator values for intrastrata levels of productive horizons and for the section fragment of SDKhZ field have been developed.

Advances in the Application of Nanofluids Molecular Dynamics in Oil and Gas Field Development

Molecular dynamic (MD) simulation has been widely applied to various technical fields, especially in oil-gas field development in recent years. The MD simulation of nanofluids is elaborated from the aspect of nanofluid properties research via MD, the self-assembling MD simulation of nanoparticles at O/W two-phase interface, and the flow simulation of nanofluids in microscopic pores. Finally, theoretical guidance is provided for the application of MD in oilfield development to foster strengths and circumvent weaknesses.

Improvement Dependability of Offshore Horizontal-Axis Wind Turbines by Applying New Mathematical Methods for Calculation the Excess Speed in Case of Wind Gusts

The problem of increasing the reliability of wind turbines exists in the development of new offshore oil and natural gas fields. Reducing emergency situations is necessary due to the autonomous operation of drilling rigs and bulk seaports in the subarctic and Arctic climate. The relevance of the topic is linked with the development of a methodology for theoretical and practical studies of gas dynamics when gas flows in a pipe, based on a mathematical model using new mathematical methods for calculation of excess speeds in case of wind gusts. Problems in the operation of offshore wind turbines arise with storm gusts of wind, which is comparable to the wave movement of the gas flow. Thus, the scientific problem of increasing the reliability of wind turbines in conditions of strong wind gusts is solved. The authors indicate a gross error in the calculations when approximating through the use of the Fourier series. The obtained results will allow us to solve one of the essential problems of modeling at this stage of its development, namely: to reduce the calculation time and the adequacy of the model built for similar installations and devices. Experimental studies of gas-dynamic flows are carried out on the example of a physical model of a wind turbine. In addition, a computer simulation of the gas-dynamic flow process was carried out. The use of new approximation schemes in processing the results of experiments and computer simulation can reduce the calculation error by 1.2 percent.

Did Wastewater Disposal Drive the Longest Seismic Swarm Triggered by Fluid Manipulations? Lacq, France, 1969–2016

ABSTRACT The activation of tectonics and anthropogenic swarms in time and space and size remains challenging for seismologists. One remarkably long swarm is the Lacq swarm. It has been ongoing since 1969 and is located in a compound oil–gas field with a complex fluid manipulation history. Based on the overlap between the volumes where poroelastic model predicts stresses buildup and those where earthquakes occur, gas reservoir depletion was proposed to control the Lacq seismic swarm. The 2016 Mw 3.9, the largest event on the site, is located within a few kilometers downward the deep injection well. It questions the possible interactions between the 1955–2016 wastewater injections and the Lacq seismicity. Revisiting 60 yr of fluid manipulation history and seismicity indicates that the impacts of the wastewater injections on the Lacq seismicity were previously underevaluated. The main lines of evidence toward a wastewater injection cause are (1) cumulative injected volume enough in 1969 to trigger Mw 3 events, onset of Lacq seismicity; (2) 1976 injection below the gas reservoir occurs only a few years before the sharp increase in seismicity. It matches the onset of deep seismicity (below the gas reservoir, at the injection depth); (3) the (2007–2010) 2–3 folds increase in injection rate precedes 2013, 2016 top largest events; and (4) 75% of the 2013–2016 events cluster within 4–8 km depths, that is, close to and downward the 4.5 km deep injection well. As quantified by changepoint analysis, our results suggest that timely overlaps between injection operations and seismicity patterns are as decisive as extraction operations to control the Lacq seismicity. The seismicity onset is contemporary to cumulative stress changes (induced by depletion and injection operations) in the 0.1–1 MPa range. The interrelation between injection and extraction is the most probable cause of the Lacq seismicity onset and is sustenance over time. The injected volume–largest magnitude pair for Lacq field is in the same range (90% confidence level) than wastewater volume–magnitude pairs reported worldwide, in a wide variety of tectonic settings.

MULTICRITERIA DECISION-MAKING IN THE SELECTION OF WARSHIPS: A NEW APPROACH TO THE AHP METHOD

The budgetary constraints for the Brazilian Navy (BN) have caused several negative effects, resulting in an undersized fleet, decreasing the capacity to protect marine oil and natural gas fields, combat marine pollution from ships, and monitor other illegal activities at sea and inland waters. This paper aims to choose a medium-sized warship to be built by the BN, through the application of the Analytic Hierarchy Process (AHP) method. After a bibliometric study on Multiple-Criteria Decision-Making (MCDM), the AHP was chosen as the most appropriate method for the proposed case study. We analyzed three ship projects with regard to nine operational and economic criteria, taking into account the evaluations of BN officers with recognized experience and knowledge in military operations. We also introduced a sensitivity analysis based on the relationship between standard deviation and mean scores in order to verify and increase the reliability of the ranking. As a result, the methodology suggested that the best option is to build a brand-new ship with more significant modernizations to provide for the operational needs of the BN.

Environmental improvement based on advancement of water injection technologies

The processes of produced water control in oil-gas industry lead to the periodical environmental improvement. Proceeding intensive oil development in Absheron peninsula throughtout over 150 years led to the increase of flooding percentage and oil decrease in geological reservoir. Therefore, due to the fact that the capacity of produced water together with oil exceeds for several times the total capacity of extracted oil, the issues associated with the further recycling and systematic control on produced water are particularly topical. The implementation of fully closed system of produced water control formed in the oil and gas development in Absheron territory is considered the need of the hour. It is necessary to study the current ecological situation in oil-gas fields, increase the production efficiency and reduce the impact on environment, offering more improved methods based on up-to-date scientific and methodological analysis. The reduction of produced water capacity and gradual environmental improvement may be achieved due to the decrease of operation of highly flooded wells in the old oil-gas fields. Due to the produced water deposition from the oil in the sedimentary rocks and scavenger wells, the amount of oil in the water reduced for several times, and in this case it is possible to reduce the effect of hydrocarbons on the soil, water and atmosphere.

Geodynamic processes, hydrocarbon migration and their occurrence in geophysics

The paper shows that in the oil deposits formed in the Earth crust, due to the overpressure hydrocarbon components migration to the sedimentary cover and penetration to the field occur. As a result of vertical hydrocarbon migration in the oil and gas fields, a subvertical zone differing by its physical properties from the environment is formed. Such a subvertical zone affects geophysical, geochemical and logging data as well. Therefore, while migrate to the near-surface zone, hydrocarbons interact with a complex of rocks of sedimentary cover. As a result of impacting of fines forming hydrocarbons with the complex of subsurface rocks, a part of hydrocarbon flow energy transforms into the fluctuations of minor particles of subsurface rocks, and the other one, in the result of atoms and molecules impact - into the irregular molecule motion. A part of mechanical energy of moving particles transforms into another - thermal type of energy, as a result of which the environment gets “warmed”. Herewith, the temperature in near-surface zones differs from environment. Therefore, in the oil and gas fields in subvertical zones a heterogeneous area differing from the environment by geophysical, geochemical and other characteristics is formed. Based on the research data carried out by numerous specialists, it was justified that the changing of geophysical parameters is affected not only by oil-gas field, but near-surface zone as well. This feature is recommended to consider in the analysis of geophysical data.

Lithological characteristics of modern sediments in the southwestern part of the Kara Sea shelf

In August - September 2020, during cruise 49 of the R/V Akademik Nikolay Strakhov , comprehensive geological, geophysical, hydroacoustic, geomorphological and hydrophysical research studies of the western segment of the Arctic zone within the Pechora and Kara Seas began in 2018-2019 were continued. As previously, the work was aimed at mapping the relief and modern sediments in order to assess the possible negative consequences of changes in natural conditions on the Arctic coast of the Russian Federation. The main purpose of the research was to assess the evolution of natural environments within the southwestern part of the Kara Sea shelf in connection with the observed global climate change in the Arctic, as well as with the expected increase in anthropogenic load on the Arctic shelf due to the development of oil and combustible natural gas fields. Bottom grab and a shock ground tube were used to obtain samples of recent sediments of the Kara Sea. The sampling sites were determined based on the analysis of data from bathymetric bottom survey and continuous seismic profiling. During the research, the boundaries of the distribution of various facies of bottom sediments within the southwestern part of the Kara Sea shelf have been clarified. The main feature of the modern bottom sediments in the southwestern part of the Kara Sea shelf is a wide areal distribution of thin facies - pelitic muds. Along the eastern and southern coasts of the Archipelago Novaya Zemlya, a distribution zone of iceberg sediments with a width of at least 150 km has been established. The formation of icebergs should be associated with the movement of the Novaya Zemlya cover glacier, formed 30-20 thousand years ago during the Sartan Ice Age. As the studies have shown, the general Holocene transgression in the Kara Sea was periodically replaced by short regressions, at least in the southwestern part of the basin.

Research on the Flow Characteristic in a Multi-Stage Multiphase Pump by Numerical Simulations

As a cost-effective option for subsea gas and oil fields development, multiphase pump has been widely used and plays an important role in promoting field production especially for those brownfields. The objective of this research is to study the variations of flow parameters at the inlet of each stage in a five-stage helico-axial pump under design conditions by using commercial CFD packages. The numerical results show that inlet volume flow rate, gas volume fraction (GVF) and flow angle of each stage both decreases from the first stage to the fifth stage because of the compression. The variations of these parameters along the flow direction are susceptible to the effect of rotational speed and initial gas volume fraction at inlet of the first stage. These inlet flow parameters from inlet to outlet of the five-stage pump just change little when the initial inlet GVF is lower than 10% or higher than 90%. While the variation is obvious when inlet GVF is from 20% to 80%. Based on numerical simulation results, the stage-by-stage design method is proposed and geometry parameters such as inlet impeller hub diameter and inlet angle of blade in the second stage are modified according to its inlet flow conditions. The comparison results between the modified pump and original pump show that pressure distribution at leading edge of impeller blades in each stage becomes uniform in the modified multistage pump. The inlet incident flow loss of each stage is diminished and internal flow conditions has been significantly improved. Thus, the pump’s boosting capacity is enhanced. These research results in this paper are instructive for the performance optimization of multistage pumps used in gas oil fields.

The effects of lithology and facies types on the anisotropy parameters and upscaling factor of the sand reservoirs in the deep-water Sadewa field, Kutei Basin, East Kalimantan, Indonesia

Abstract The anisotropy and upscaling factors adjustment are very important in the proper integration of the core ultrasonic and log sonic data for hydrocarbon reservoir characterization. Related to this issue, this paper evaluates the effects of the lithology and facies types on the anisotropy parameters and upscaling factor. The data are taken from the deep-water oil-gas Sadewa field located in the Kutei Basin, East Kalimantan, Indonesia at water depths of 500–750 m. The main reservoirs in this field are the Upper Miocene sand reservoirs deposited in the upper slope fan and channel facies. Fifty core plugs sampled at depths around 3000–4000 m were collected for thin-section petrography analysis and ultrasonic measurements. The thin-section petrography analysis shows that both facies areas are dominated by greywackes with parallel lamination structure and/or intergranular porosity. The 1 MHz ultrasonic velocities were measured in the 50 core plugs. Meanwhile, 10–40 KHz dipole sonic log data sampled at the same plug’s depth positions were used to calculate the elastic (Vp, Vs, Poisson ratio, etc) and Thomsen’s e, γ and δ anisotropy parameters. The results show that for the parallel lamination and intergranular porosity greywacke samples, e parameter is the best for compensating the anisotropy effect in the integrated core and log data reservoir quality determination (sand shale ratio, percentage of quartz contents, the effective and the total porosities). However, when the samples are non-intergranular porosity greywacke, the anisotropy effect in the core-log data correlation, is too irregular to be compensated by any elastic and anisotropy parameter. The core-log data upscaling factor in the channel facies is much smaller than the upper slope fan facies, and it is in line with the gamma-ray log data which indicates that the sandy channel facies is more homogeneous than the intercalated shale-sand upper slope fan facies. The overall results suggest that the lithology and facies types significantly affect the anisotropy parameters and upscaling factor. In addition, the best elastic or anisotropic parameters) should be determined to minimize the effects in the core and log data integration for hydrocarbon reservoir characterization.

Test Results for Ventilation Units

The article presents the findings of the tests conducted for the forced air heating unit of a supply ventilation system. The supply air system is designed to feed clean air into the industrial facility of the oil-gas field of the Yamalo-Nenets Autonomous District. The tests were performed in five modes at the ambient air temperatures of -5, -10, -15, -20, -25 °C. The mode throughout the tests was steady, i.e. the temperatures of water and air remained unchanged within 30 minutes before the tests. Since the capacity of the heater unit was proved to be 24 - 41.5% according to the test results, recommendations were made to improve the capacity. With the said measures having been taken, control measurements of test parameters were carried out, the actual U-value was calculated and the capacity of the heater unit was determined. The performed work is relevant in view of theoretical and practical significance for engineers and employees of industrial enterprises servicing the ventilation systems.

Acid Fracturing Optimizing Design and Application in Deep Naturally Fractured Carbonate

More than 30% of carbonate reservoirs in the Tarim oilfield and XiNan oil-gas field are naturally fractured-vuggy reservoirs, of which the production is high in most cases and economic returns can be achieved within a short period of time. Acid fracturing is one of the key technology for development of such naturally fractured-vuggy reservoirs. Mud overflow and loss may be emerged at the same time while drilling fractured-vugular carbonate, once it happened, the well control will become complicated. So, the wellbore is drilled a certain distance up or transversal to these huge caves or natural fractures, and acid fracturing will be executed to connected the reservoirs to obtain the hydrocarbon in the reservoir. Acid-fracturing design of fractured-vugular carbonate is based on the relationship between the wellbore and fractured-vugular reservoirs. The acid fracturing design in naturally fractured-vuggy carbonate reservoir is different from the conventional one, it should be optimized based on the spatial positions of the fracture-vuggy body identified via geophysical prospecting, the wellbore and the distance between the two. In the case that the wellbore precisely reaches the top of the fracture-vuggy body, good oil and gas show or overflow is frequently happened. At this moment, drilling ceases and the wellbore are cemented and completed. The small-scale acid fracturing treatment is then carried out, and connectivity between etched fractures and the top of the fracture-vuggy body will lead to high hydrocarbon production. If a certain distance exists between the wellbore and fracture-vuggy reservoirs, 3D seismic imaging will be adopted to calculate the vertical distance between the center of the storage body and the wellbore, which is then used to optimize the injected fluid volume, pump rate and acid fracturing techniques. To create connectivity with the fracture-vuggy storage body relatively far away from the wellbore, acid fracturing involving preflush or multi-stage injection is used. Pressure drops by several ∼ several tens of MPa usually occur as the artificial fracture propagates into the fracture-vuggy body. After fracturing penetrating into the fracture-vuggy body, acid injection starts. During the early acid injection, the pump rate is raised up for longer etched length inside the fracture. It is then lowered during the late acid injection to improve the conductivity of etched fractures. If multiple fracture-vuggy bodies exist near the wellbore, the temporary diverting acid-fracturing will be treated, optimized with respect to the distance between the wellbore and different fracture-vuggy storage bodies, spatial relationship between the maximum principal stress direction and fracture-vuggy storage body and the trend of natural fractures, will be implemented to communicate with multiple naturally fractured vuggy reservoirs. This acid fracturing integrating geophysical prospecting and wellbore trajectory has been applied in hundreds of wells in the Tarim oilfield. Moreover, the success rate of such acid fracturing treatments is increasing with the advancement in the characterization of the fracture-vuggy reservoirs.

Methods of regulation of development processes of Bahar field (in the context of X horizon of Balakhany suite)

The development of oil-gas sector in Azerbaijan since the second half of the XX century was achieved mainly due to the exploitation of offshore fields. However, as a result of harsh hydro-meteorological conditions in the Caspian Sea, the exploration, as well as the development of offshore oil-gas deposits was not so easy. Exactly in such conditions due to the efforts of the scientists and experienced engineers and technicians specialized in this sphere, the hard exploration problem was solved both from geological and technical points of view. However, even today there are some technological and geological-technical issues during the operation of offshore oil-gas fields or in whole development of the resources. From this point of view Bahar field as the all fields being in long-term operation still have a large capacity of unused residual reserves of great importance. Therefore, accurate and detailed study of complicated oil recovery processes is a significant and current task. Thus, for the analysis of oil recovery processes it is necessary to select the optimum and economically feasible methods and practical to involve into the investigation dynamic model of “Stewhart control charts” for its solution.

Proposal of a stage-by-stage design method and its application on a multi-stage multiphase pump based on numerical simulations

Rotodynamic multiphase pumps are usually equipped with many compression units to provide sufficient boosting pressure for the transportation of production fluid in gas oil field. It is a challenge to maintain pump performance while flow parameters in each stage vary due to the compressibility of gas-liquid phase. In this article, a stage-by-stage design method is proposed to improve the boosting capability of a multiphase pump. Variations of flow parameters in each stage are investigated based on computational fluid dynamics (CFD) numerical simulation. Available methods to determinate main impeller geometry parameters of impeller are discussed. The stage-by-stage design method is applied on a five-stage multiphase pump when the inlet gas volume fraction (GVF) are 30% and 50% separately. The second stage is modified base on its corresponding inlet flow parameters when inlet GVF is 30% while the second and third stage are modified when inlet GVF is 50%. Flow parameters, pressure distribution and velocity distribution are compared between the original pump and modified pump. Differential pressure of the modified pump increases by 53.72 kPa and 58.57 kPa respectively when inlet GVFs are 30% and 50%. The feasibility of the stage-by-stage design method is verified through the comparison results.

Differences and Constraints of Varying Gas Dryness Coefficients in the Cainan Oil-Gas Field, Junggar Basin, Nw China

Differences and Constraints of Varying Gas Dryness Coefficients in the Cainan Oil-Gas Field, Junggar Basin, Nw China

On the Way of Policy Making to Reduce the Reliance of Fossil Fuels: Case Study of Iran

Nowadays, fossil fuels are well known as a predominant source of energy in the planet. Located in the Middle East region, Iran holds one of the largest fossil fuel reservoirs in the world. The country has abundant oil and natural gas fields in various regions; some of them are shared between other countries and have not reached their operational capacity yet. Meanwhile, during recent years and due to global warming followed by environmental global contracts such as Kyoto protocol, using fossil fuels is being criticized to a large extent around the world. Therefore, the global interest has been focused toward clean energy resources. Furthermore, endowed with sundry geographical pattern throughout its land, Iran has adequate renewable energy potentials. So, there will be a serious paradox affecting its whole energy policy: more exploration and extraction of conventional fossil fuels or take advantage of renewable and sustainable energy resources? In this paper, energy structure of Iran is generally overviewed, followed by study of renewable energy potentials in various parts of the country. Afterwards, policy making in renewable energy market, systems, and applicable strategies are elaborated. Furthermore, a number of barriers obstructing the development path of renewable energy schemes and initiatives are presented and discussed in detail.

Composite tube damage evaluation in aggressive oil-gas field

The purpose of this article is to lead a research program to assess the damaging of liners of a composite tube for operation in oil-gas fields containing carbon dioxide, including those with minor amounts of hydrogen sulfide at standard conditions and under conditions of elevated temperature and pressure. To assess the level of corrosion resistance of the composite tube liner, stress corrosion cracking tests were carried out, autoclave tests for general corrosion at elevated temperatures and pressures were also carried out, and electrochemical studies were carried out to assess the equilibrium corrosion potential and calculate corrosion rates analyzing Tafel curves.

Regulation of financial guarantees relating to the decommissioning of oil and natural gas fields

Regulation of financial guarantees relating to the decommissioning of oil and natural gas fields

On the efficiency of integrated analysis of parameters of ref- racted and reflected waves in prediction of oil-gas bearing of section

Based on the comparative analysis of results of researches carried out via the methods of reflected and refracted waves with the purpose of prediction of geological section, the paper justifies that one of the major evidences in the field of seismic wave in oil-gas fields of geological section is the differentiation of elastic properties of oil-gas bearing reservoirs from the environment. Based on mutual comparison of results of conducted researches, it is shown that in the prediction of geological section the integ- rated analysis of changes of dynamic parameters of the waves reflected from the surface of oil-gas bearing reservoir and transmitted through this surface may further increase the reliability of obtained results. The research surveys carried out in Naftalan-Shimali Naftalan areas via the methods of reflected and refracted waves were simultaneously analyzed. With the aim of comparative analysis, the deposit type anomalies revealed through the method of refracted waves were compared to the results of attributed analysis of seismic cross-sections obtained with the method of common depth point. The correspondence of the signs associated with the oil-gas bearing content in change of dynamic parameters of refracted and reflected waves has been specified. With the purpose of prediction of geological section, a complex research is proposed.