A New Methodology Combining Geophysical Calculations and Geological Analysis to Identify and Characterize Carrier Systems for Vertical Hydrocarbon Migration in the Central Diapir Zone of the Yinggehai Basin, China

To understand hydrocarbon migration in terms of the mechanisms, accumulations and exploration targets, it is essential to correctly identify and characterize the carrier systems that control fluid-migration history and oil/gas reservoir formation. The Yinggehai Basin in China is an important area for natural gas exploration and production. However, due to the argillaceous sand sedimentary environment and the absence of faults from the Neogene thermal subsidence period, traditional migration pathways are absent in the Yinggehai Basin, posing significant challenges to target evaluation in this area. Exploration shows that most of the existing gas reservoirs are associated with vertical migration. In this work, coherence cube and curvature seismic techniques are used in the central diapir zone of the Yinggehai Basin to identify diapir-associated fractures and regional stress. Together with geological analysis, two categories of carrier system are discussed in detail to explain the complex migration and accumulation patterns that have puzzled the area. Diapirs have five evolutionary phases, i.e., pressurization, piercing, equilibrium, release and collapse, which have different fracture development patterns, leading to different mechanisms of hydrocarbon migration and accumulation. The carbon isotopes of gaseous hydrocarbons in DF shallow layers and mid-deep layers have an inverted order distribution, indicating mixed accumulation with different maturity, whereas in the mid-deep layers of the diapir-affected areas, there is a single accumulation with low maturity. Early diapiric activity allowed the natural gas produced from deep source rocks to migrate upward along the diapiric carrier system and accumulate in suitable traps to form gas reservoirs. For regional-stress related fractures, the gradual loss of overpressure and fluids from deep to shallow in high-pressure fractures results in the gas accumulation time of deep traps in the regional stress-related carrier system being relatively late and the gas accumulation time of shallow traps being relatively early

A New Methodology Combining Geophysical Calculations and Geological Analysis to Identify and Characterize Carrier Systems for Vertical Hydrocarbon Migration in the Central Diapir Zone of the Yinggehai Basin, China

To understand hydrocarbon migration in terms of the mechanisms, accumulations and exploration targets, it is essential to correctly identify and characterize the carrier systems that control fluid-migration history and oil/gas reservoir formation. The Yinggehai Basin in China is an important area for natural gas exploration and production. However, due to the argillaceous sand sedimentary environment and the absence of faults from the Neogene thermal subsidence period, traditional migration pathways are absent in the Yinggehai Basin, posing significant challenges to target evaluation in this area. Exploration shows that most of the existing gas reservoirs are associated with vertical migration. In this work, coherence cube and curvature seismic techniques are used in the central diapir zone of the Yinggehai Basin to identify diapir-associated fractures and regional stress. Together with geological analysis, two categories of carrier system are discussed in detail to explain the complex migration and accumulation patterns that have puzzled the area. Diapirs have five evolutionary phases, i.e., pressurization, piercing, equilibrium, release and collapse, which have different fracture development patterns, leading to different mechanisms of hydrocarbon migration and accumulation. The carbon isotopes of gaseous hydrocarbons in DF shallow layers and mid-deep layers have an inverted order distribution, indicating mixed accumulation with different maturity, whereas in the mid-deep layers of the diapir-affected areas, there is a single accumulation with low maturity. Early diapiric activity allowed the natural gas produced from deep source rocks to migrate upward along the diapiric carrier system and accumulate in suitable traps to form gas reservoirs. For regional-stress related fractures, the gradual loss of overpressure and fluids from deep to shallow in high-pressure fractures results in the gas accumulation time of deep traps in the regional stress-related carrier system being relatively late and the gas accumulation time of shallow traps being relatively early

The timescale of plume-driven cratonization: A complete record from Tarim

ABSTRACT: Cratonization of the Tarim block in central Asia is finalized by the Permian Tarim plume that welded two cratonic nuclei together. Hence, the over-10-km-thick Tarim basin preserves a complete record of deformation and growth strata before, during, and after the plume-driven cratonization. Here we use seismic reflection data from the central Tarim basin to quantify the timing and style of the Paleozoic–Mesozoic deformation. The thrust and strike-slip faults there all underwent an early, intense deformation stage in the earliest Ordovician–Middle Devonian, a hiatus stage from Late Devonian to Late Permian, and a newly-discovered stage of weak activity throughout the Mesozoic. The intracontinental deformation is controlled by the subduction and accretion surrounding the Tarim block. The minor, but non-zero, Mesozoic strains reflect the ongoing adjustment to far-field compressions during the cooling and strengthening of the plume-stitched continental lithosphere. The cessation of interior deformation marks that the Tarim cratonization is finally attained ~200 Myr after the plume waned

Geothermal Geological Characteristics and Genetic Model of the Shunping Area along Eastern Taihang Mountain

Knowledge about subsurface geological characteristics and a geothermic genetic model plays an essential role in geothermal exploration and resource assessment. To solve the problem in the Shunping area along eastern Taihang Mountain, geothermal geological conditions were analyzed by geophysical, geochemical, and geological methods, such as magnetotelluric, gas geochemistry, and structural analysis. The geothermic genetic model was developed by analyzing the characteristics of the heat source, water source, migration channel, reservoir, and cap rock of the geothermal geological conditions. Favorable deep thermal conduction conditions and sufficient atmospheric precipitation in the study area provide an original heat source and water supply for geothermal formation. The faults and unconformities of different scales have become effective channels for the migration of underground hot water. The thermal reservoir formed by marine carbonate rocks with karst fissure development provides suitable space for the storage of underground hot water. Although the Cenozoic strata have good thermal insulation and water insulation function, the thermal insulation and water insulation effect is not ideal because of the shallow coverage in the Shunping area and the damage by tectonic action, which affected thermal insulation and water insulation to some extent, restricting the practical preservation of underground heat energy in the Shunping area. The bedrock geothermal resource in the Shunping area is original from the combined action of multiple indexes of source, transport, reservoir, and cap. The geothermal geologic conditions of source and reservoir in the Shunping area are very similar to those in the Xiongan new area, and have obvious advantages in hydrodynamic conditions. Although limited by the cap’s effectiveness, the geothermal resources in the Shunping area can provide some clean energy support for local production and life, thereby satisfying economic development conditions and encouraging further geological exploration

In-situ stress prediction in ultra-deep carbonate reservoirs of Fuman Oilfield, Tarim Basin of China

The Fuman Oilfield in Tarim Basin has great potential for ultra-deep carbonate oil and gas resources, and is an important area for future storage and production increase. The present-day in-situ stress field is critical during the exploration and development. However, no systemic investigations have been carried out in this oilfield. Therefore, in this study, the present-day in-situ stress field in the Ordovician carbonate reservoir is predicted and analyzed based on well log calculation and geomechanical numerical modeling. The results indicate that, 1) NE-SW-trending is the dominant horizontal maximum principal stress (SHmax) orientation. The vertical principal stress is the maximum principal stress, showing the Ordovician reservoir is under a normal faulting stress regime. 2) The distribution of in-situ stresses in the Ordovician carbonate reservoir is heterogeneous, which is mainly controlled burial depth and fault/fracture development. High stress magnitudes in the Yingshan Formation are mainly in the southeastern part of Fudong area, Fuman Oilfield. The present-day horizontal differential stress mainly ranges from 27 MPa to 30 MPa in the Yingshan carbonate reservoir. iii) Natural fractures are generally stale under the present-day in-situ stress state. Fractures that parallel to the SHmax orientation with high fracture dip angle are easier to be reactivated. The results are expected to provide geomechanical references for further oil and gas development in the Fuman Oilfield of Tarim Basin

A Review Of Fault Sealing Behaviour And Its Evaluation In Siliciclastic Rocks

Faults can be either conduits or retarders for fluid flow. As the presence of faults increases the risks for hydrocarbon exploration, the sealing behaviour of a fault zone has been a focus for geological studies in the past 30 years. Due to the widespread occurrence of fault zones, either in extensional or contractional regimes, knowledge about the fault sealing behaviour is of great importance to a wide spectrum of disciplines in geosciences, for instance, structural geology, geochemistry, petroleum geology, etc. Geologists have extensively studied the sealing properties of a fault zone over the last decades, ranging fromfault zone architecture, fault seal types, fault seal processes, fault rock classification, research methods and controlling factors. Although there have not been universal agreements reached on the fault seal classifications, two types of fault seals have already been recognised, which are juxtaposition seals and fault rock seals. The early foundation of Allanmap and triangle juxtaposition diagramallows the investigation on the effects of stratigraphic juxtaposition between hanging wall and footwall on the sealing properties of a fault zone. The study on the detailed fault zone architecture also implies the importance of fault arrays that increase the complexity of overall stratigraphic juxtaposition between hangingwall and footwall. The fault seal processes and their generated fault rocks play an important control on sealing properties of a fault zone. Temperature and stress history, which are closely related to burial history, are also found to control the sealing capacity of a fault zone to some extent. The methods such as stratigraphic juxtaposition, clay smear indices, microstructural analysis and petrophysical assessment have significantly boosted the research of fault sealing behaviour. However, further research is still needed to increase the effectiveness of present fault seal analysis