Natural Fractures in Low-Permeability Sandstone Reservoirs in the LD-A HPHT Gas Field, Yinggehai Basin: Implications for Hydrocarbon Exploration and Development

Li, Hui; Fan, Caiwei; Jiang, Zhenxue; Li, Jun; Li, Chao; Xu, Xuhui; Li, Fang; Hu, Gaowei

doi:10.3389/feart.2022.934097

Cited by 4 publications

(3 citation statements)

References 44 publications

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“…Samples from Dongfang and Ledong areas of Yinggehai Basin are deeply buried, taken from 2,994 to 3,634 m respectively. Within this depth range, the formation develops abnormally high fluid pressure and temperature (Li et al, 2022), the formation pressure coefficient is 1.5-2.2, and the temperature gradient is 37-50 °C/km. Parameters in the experiment were set to simulate changes in real geological conditions as much as possible.…”

Section: Experimental Scheme Of Triaxial Compression Testmentioning

confidence: 98%

Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity

Jia

Jin

et al. 2023

Front. Earth Sci.

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Mudstone is the most common cap rock in petroliferous basins. The mechanical properties of mudstone in different areas and buried depths are obviously different, which directly affects the brittleness and ductileness of caprock and its deformation characteristic. This research carried out X ray diffraction (XRD) rock mineral composition analysis, microscopic observation of mineral structural characteristics and rock mechanics triaxial compression tests under different conditions on six groups of mudstone samples from three basins. On this basis, establish numerical model to simulate the fracture deformation of mudstone under geological conditions, and to clarify the influence of different factors on the rock mechanics of mudstone. Compare and analyze the fracture characteristics and stress-strain curves of mudstone samples after the test show that, the confining pressure is the most direct factor affecting the mechanical properties and deformation mechanism of mudstone in the range of oil and gas enrichment depth. Although the formation temperature has a certain influence on the rock deformation, the effect is very limited, and it is difficult to have an essential influence on the rock deformation without the action of confining pressure. The mineral composition of mudstone is also one of the main factors affecting the mechanical deformation of rock. The comparison between the content of main minerals and the mechanical parameters of rock shows that the mechanical properties of rock and the transformation of brittleness and ductileness of mudstone have the most obvious correlation with clay minerals. Numerical simulations show that, pore fluid pressure is an important factor that cannot be ignored in overpressured caprocks. Higher pore fluid pressure can significantly inhibit the transition process of rock brittleness and ductileness, and at the same time affect the fracture mode of mudstone, which is of great significance for the evaluation of caprock integrity.

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Section: Experimental Scheme Of Triaxial Compression Testmentioning

confidence: 98%

Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity

Jia

Jin

et al. 2023

Front. Earth Sci.

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“…Currently, the subdivision of reservoir layers is mainly focused on the subdivision of single sand bodies. In a narrow sense, the flow unit is a further subdivision of the reservoir based on the rock properties that affect the fluid flow after subdividing a single sand body, and a completely different standard is adopted by subdividing a single sand body [16][17][18][19][20][21][22][23][24]. Among these, the FZI method is widely used.…”

Section: Influence Of Pore Structure On Permeabilitymentioning

confidence: 99%

A Method for Evaluating Reservoir Permeability Based on Machine Learning Flow Unit Index

Cheng,

Zhao,

Gao

et al. 2023

Lithosphere

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The H formation of the Y gas field in the X depression belongs to a low-permeability tight sandstone reservoir affected by sedimentation, diagenesis, and cementation. The lithology and pore structure of the target layer are complex, with strong physical heterogeneity and complex pore-permeability relationships. Conventional core pore permeability regression and nuclear magnetic resonance software-defined radio methods do not satisfy the requirements for precise evaluation in terms of permeability calculation accuracy. Based on the principle of the flow zone index (FZI) method, this study analyzed the influence of pore structure on permeability and extracted three pore structure characterization parameters, namely, the maximum pore throat radius (Rmax), displacement pressure (Pd), and average throat radius (R), from the mercury injection capillary pressure curve. The relationship between the FZI and pore structure is clarified. Therefore, the FZI in this area can characterize the permeability differences within different flow units. Based on the flow unit theory, a refined evaluation model for three types of reservoirs was established in the study area. By analyzing the response characteristics and correlation of conventional logging curves using machine learning, three optimization combination curves were selected, and a multiparameter fitting equation for the FZI was established, which was applied to predict the permeability of new wells. The results showed that the calculated permeability was highly consistent with the core analysis results, thereby providing a theoretical basis for the precise evaluation of low-permeability tight reservoirs.

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“…The formation and evolution of fractures include a large amount of information related to rock mechanics and determine the physical properties and oil-gas properties of low-permeability reservoirs (Germanovich et al, 1994;Wang et al, 2008;Zhang et al, 2020;Li et al, 2022). Rock strength, petrology, and tectonic stress influence the development of natural fractures in low-permeability reservoirs Li et al, 2022), and fracture density and opening directly controlled gas productivity. Microfractures with apertures less than 50 μm improve porosity and permeability in these reservoirs (Wang et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Relationship between the heterogeneity of low-permeability reservoirs and the dynamic evolution of fractures under uniaxial compression conditions by CT scanning: A case study in the jiyang depression of Bohai Bay Basin, China

Shi

Zhang

et al. 2023

Front. Earth Sci.

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Based on an analysis of core fractures and computed tomography scanning by X-ray under uniaxial compression tests with loading and unloading, this study investigated the three-dimensional evolution of fracture initiation and propagation in different heterogeneity conditions of low-permeability reservoirs. Reservoir heterogeneity affected the 3D dynamic development of fractures. With increasing loading value, fractures with strong heterogeneity in low-permeability reservoirs followed the development sequence from shallow to deep depth in the profile. When the fracture tip reached the incompetent layer, propagation stopped. Subsequently, when the deformation continued to increase, the fracture crossed the incompetent layer and initiated a new fracture at the front end. Therefore, the across-bedding and through-going macro fractures formed in conjugate sets or were Y-shaped, with roughly equal spacing. In the plane, the fractures initiated along the pre-existing bedding parallel fracture and further propagated into large fractures. Consequently, they formed a net-shaped fracture from the edge to the center, with a long development period. These fractures intersected to form a complex, interconnected, and high-fracture-density system in three dimensions. Under the same loading value, owing to uniform lithology, the formation of micro-fractures in the weak heterogeneity of low-permeability reservoirs is difficult. Furthermore, long shear fractures were only produced in a relatively short formation period with a low fracture density. In the plane, the fractures stepped in an en-énchelon and terminated with horse-tailing microfractures. Moreover, the strong heterogeneity of low-permeability reservoirs was more favorable for producing fractures. The fracture volume was 13.17% of the total sample volume compared to 0.67% in the weak-heterogeneity reservoir under the same loading compression. Furthermore, a better fracturing effect was achieved by fracturing along the direction >50° with the natural fracture and under the condition of small differential horizontal stresses.

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Natural Fractures in Low-Permeability Sandstone Reservoirs in the LD-A HPHT Gas Field, Yinggehai Basin: Implications for Hydrocarbon Exploration and Development

Cited by 4 publications

References 44 publications

Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity

Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity

A Method for Evaluating Reservoir Permeability Based on Machine Learning Flow Unit Index

Relationship between the heterogeneity of low-permeability reservoirs and the dynamic evolution of fractures under uniaxial compression conditions by CT scanning: A case study in the jiyang depression of Bohai Bay Basin, China

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