scholarly journals The Impacts of Nano-Micrometer Pore Structure on the Gas Migration and Accumulation in Tight Sandstone Gas Reservoirs

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4102
Author(s):  
Juncheng Qiao ◽  
Xianzheng Zhao ◽  
Jianhui Zeng ◽  
Guomeng Han ◽  
Shu Jiang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Gas Flow ◽  
Physical Simulation ◽  
Effective Porosity ◽  
Gas Migration ◽  
Pore Throat ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Linear Flow ◽  
Small Pore

The uncertainties between reservoir quality and gas migration and accumulation in tight sandstone gas reservoirs are intrinsically attributed to complex microscopic pore structures. Integrated analysis including the physical simulation experiment of gas migration and accumulation, X-ray computed tomography (X-CT), and casting thin section (CTS) were conducted on core plug samples collected from the Upper Paleozoic Permian Lower Shihezi and Shanxi tight sandstone of the Daniudi area in the Ordos Basin to investigate the impacts of pore structure on the gas migration and accumulation. Physical simulation suggested that the gas flows in migration in tight sandstone reservoirs were characterized by deviated-Darcy linear flow and non-linear flow regimes. Minimum and stable migration pressure square gradients determined by application of apparent permeability were employed as key parameters to describe gas flow. Pore structure characterization revealed that the tight sandstone reservoir was characterized by wide pore and throat size distributions and poor pore-throat connectivity. The pore–throat combinations could be divided into three types, including the macropore and coarse throat dominant reservoir, full-pore and full-throat form, and meso-small pore and fine throat dominant form. Comparative analyses indicated that pore and throat radii determined the gas flow regimes by controlling the minimum and stable migration pressure gradients. Gas accumulation capacity was dominated by the connected effective porosity, and the gas accumulation process was controlled by the cumulative effective porosity contribution from macropores to micropores. Variations in pore structures resulted in differences in gas migration and accumulation of tight sandstone reservoirs. The macropore and coarse throat-dominant and the full-pore and full-throat reservoirs exhibited greater gas migration and accumulation potentials than the small pore and fine throat dominate form.

scholarly journals Influence of Pore Throat Structure and the Multiphases Fluid Seepage on Mobility of Tight Oil Reservoir

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Fan Zhang ◽  
Hanmin Xiao ◽  
Zhenxue Jiang ◽  
Xianglu Tang ◽  
Xuewei Liu ◽  
...  
Keyword(s):  
Water Saturation ◽  
Bound Water ◽  
Effective Porosity ◽  
Tight Oil ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Small Pore ◽  
Fluid Seepage ◽  
Phase Mobility

Abstract Mobility is the main factor restricting the production of tight oil. In order to explore the influence of pore throat structure and fluid seepage on the mobility, six tight sandstone samples are selected by high-pressure mercury intrusion, nuclear magnetic resonance, water driving oil experiments, and oil-water relative permeability experiments to discuss the influence of pore structure and multiphases on the mobility of tight oil. The results indicate that with the increase in effective porosity, more oil and water are exchanged, and the mobility of the oil phase is enhanced. The large pore is positively correlated with the mobility of tight oil while the relationship between the mobility of small pore and effective porosity remains unclear. Particularly, the mobility of the tight oil is determined by the matching relationship between the pore throat radius and the sorting of the tight reservoir. Specifically, the smaller the two-phase copermeation zone, the greater the bound water saturation; the greater the slope of the oil phase permeability curve, the less the space for the two phases to flow together; the more the oil blocked by water in the reservoir, the worse the phase mobility. The mobility of tight oil can be divided into four categories by pore throat radius, pore throat sorting coefficient, and bound water saturation.

scholarly journals Microscale Pore Throat Differentiation and Its Influence on the Distribution of Movable Fluid in Tight Sandstone Reservoirs

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Fengjuan Dong ◽  
Xuefei Lu ◽  
Yuan Cao ◽  
Xinjiu Rao ◽  
Zeyong Sun
Keyword(s):  
Ordos Basin ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Thin Sections ◽  
Small Pore ◽  
Sandstone Reservoir ◽  
Sandstone Reservoirs ◽  
Classification Evaluation ◽  
Better Than

Tight sandstone reservoirs have small pore throat sizes and complex pore structures. Taking the Chang 6 tight sandstone reservoir in the Huaqing area of the Ordos Basin as an example, based on casting thin sections, nuclear magnetic resonance experiments, and modal analysis of pore size distribution characteristics, the Chang 6 tight sandstone reservoir in the study area can be divided into two types: wide bimodal mode reservoirs and asymmetric bimodal mode reservoirs. Based on the information entropy theory, the concept of “the entropy of microscale pore throats” is proposed to characterize the microscale pore throat differentiation of different reservoirs, and its influence on the distribution of movable fluid is discussed. There were significant differences in the entropy of the pore throat radius at different scales, which were mainly shown as follows: the entropy of the pore throat radius of 0.01~0.1 μm, >0.1 μm, and <0.01 μm decreased successively; that is, the complexity of the pore throat structure decreased successively. The correlation between the number of movable fluid occurrences on different scales of pore throats and the entropy of microscale pore throats in different reservoirs is also different, which is mainly shown as follows: in the intervals of >0.1 μm and 0.01~0.1 μm, the positive correlation between the occurrence quantity of movable fluid in the wide bimodal mode reservoir is better than that in the asymmetric bimodal mode reservoir. However, there was a negative correlation between the entropy of the pore throat radius and the number of fluid occurrences in the two types of reservoirs in the pore throat radius of <0.01 μm. Therefore, pore throats of >0.1 μm and 0.01~0.1 μm play a controlling role in studying the complexity of the microscopic pore throat structure and the distribution of movable fluid in the Chang 6 tight sandstone reservoir. The above results deepen the understanding of the pore throat structure of tight sandstone reservoirs and present guiding significance for classification evaluation, quantitative characterization, and efficient development of tight sandstone reservoirs.

Application of NMR Technology on Test of Movable Fluid Saturation of Tight Sandstone Gas Reservoir

2015 ◽  
Vol 1092-1093 ◽  
pp. 1361-1365
Author(s):  
Hong Xia Ming ◽  
Wei Sun ◽  
Ping Wu
Keyword(s):  
Pore Structure ◽  
Transverse Relaxation Time ◽  
Single Peak ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Fluid Saturation ◽  
Structure Heterogeneity ◽  
Spectrum Distribution ◽  
The Difference

The difference of movable fluid saturation of tight sandstone gas reservoir is researched, with transverse relaxation time (T2) distribution derived from nuclear magnetic resonance technique (NMR). This article newly calculate T2 cutoff value and elaborate the influence of pore structure on the occurrence characteristics of movable fluid. The study had revealed T2 spectrum distribution includes the following types: (1) wide and flat single peak; (2) left single peak; (3) high left peak with low right peak. Movable fluid saturation is low, with class IV and class V movable fluid mainly. Pore structure control properties and percolation ability of rock reservoir and whether oil could be driven out depends on throat parameters of interconnected pores. Movable fluid saturation is low with bigger pore throat ratio, narrower pore throat distribution and higer pore structure heterogeneity.

scholarly journals Petrophysical Characterizations of Shale Gas Reservoirs of the Ranikot Formation in the Lower Indus Basin, Pakistan

2021 ◽  
Vol 3 (2) ◽  
pp. 103-107
Author(s):  
Kazunori Abe ◽  
Nouman Zobby ◽  
Hikari Fujii
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Density Functional ◽  
Gas Flow ◽  
Slip Flow ◽  
Indus Basin ◽  
Size Distributions ◽  
Gas Reservoirs ◽  
Lower Indus Basin ◽  
Pore Size Distributions

The complex pore structure with nano-pores of shale gas reservoirs has an impact on the hydrocarbon storage and transport systems. We examined the pore structure of the shales of the Ranikot Formation in the Lower Indus Basin, Pakistan to investigate the full scaled pore size distributions by using a combination of techniques, mercury injection capillary pressure analysis and low pressure gas adsorption methods using N2 and CO2. Isotherm curves obtained N2 and CO2 adsorptions were interpreted using density functional theory analysis for describing the nano-scaled pore size distributions. The pore geometry of the shales was estimated to be slit-type from the isotherm hysteresis loop shape. The pore size distributions determined the density functional theory showed the dominant pore size of below around 10 nm. The Micro-scale effects such as slippage and adsorption/desorption also significantly influence the gas flow in nano-pore structure. The gas flow regimes in shales are classified into four types Darcy flow, slip flow, transition flow, Knudsen flow based on the value of the Knudsen number. Applying the specific reservoir conditions in Ranikot shale and pore size distribution to the Knudsen number, the gas flow regimes of the Ranikot shales were estimated mostly within the transition and slip flow.

scholarly journals Pore throat characteristics of tight reservoirs by a combined mercury method: A case study of the member 2 of Xujiahe Formation in Yingshan gasfield, North Sichuan Basin

2021 ◽  
Vol 13 (1) ◽  
pp. 1174-1186
Author(s):  
Youzhi Wang ◽  
Cui Mao ◽  
Qiang Li ◽  
Wei Jin ◽  
Simiao Zhu ◽  
...  
Keyword(s):  
Pore Structure ◽  
Distribution Range ◽  
Contribution Rate ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Xujiahe Formation ◽  
Mercury Injection ◽  
Tight Reservoirs ◽  
Sandstone Reservoirs

Abstract The complex pore throat characteristics are significant factors that control the properties of tight sandstone reservoirs. Due to the strong heterogeneity of the pore structure in tight reservoirs, it is difficult to characterize the pore structure by single methods. To determine the pore throat, core, casting thin sections, micrographs from scanning electron microscopy, rate-controlled mercury injection, and high-pressure mercury injection were performed in member 2 of Xujiahe Formation of Yingshan gasfield, Sichuan, China. The pore throat characteristics were quantitatively characterized, and the distribution of pore throat at different scales and its controlling effect on reservoir physical properties were discussed. The results show that there are mainly residual intergranular pores, intergranular dissolved pores, ingranular dissolved pores, intergranular pores, and micro-fractures in the second member of the Xujiahe Formation tight sandstone reservoir. The distribution range of pore throat is 0.018–10 μm, and the radius of pore throat is less than 1 μm. The ranges of pore radius were between 100 and 200 μm, the peak value ranges from 160 to 180 μm, and the pore throat radius ranges from 0.1 to 0.6 μm. With the increase of permeability, the distribution range of throat radius becomes wider, and the single peak throat radius becomes larger, showing the characteristic of right skew. The large throat of the sandy conglomerate reservoir has an obvious control effect on permeability, but little influence on porosity. The contribution rate of nano-sized pore throat to permeability is small, ranging from 3.29 to 34.67%. The contribution rate of porosity was 48.86–94.28%. Therefore, pore throat characteristics are used to select high-quality reservoirs, which can guide oil and gas exploration and development of tight sandstone reservoirs.

scholarly journals Diagenesis and its influence on reservoir quality and oil-water relative permeability: A case study in the Yanchang Formation Chang 8 tight sandstone oil reservoir, Ordos Basin, China

2019 ◽  
Vol 11 (1) ◽  
pp. 37-47 ◽  
Author(s):  
Meng Wang ◽  
Zhaomeng Yang ◽  
Changjun Shui ◽  
Zhong Yu ◽  
Zhufeng Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Relative Permeability ◽  
Oil Recovery ◽  
Ordos Basin ◽  
Reservoir Quality ◽  
Tight Oil ◽  
Property A ◽  
Tight Sandstone ◽  
Yanchang Formation ◽  
Small Pore

Abstract Different from conventional reservoirs, unconventional tight sand oil reservoirs are characterized by low or ultra-low porosity and permeability, small pore-throat size, complex pore structure and strong heterogeneity. For the continuous exploration and enhancement of oil recovery from tight oil, further analysis of the origins of the different reservoir qualities is required. The Upper Triassic Chang 8 sandstone of the Yanchang Formation from the Maling Oilfield is one of the major tight oil bearing reservoirs in the Ordos Basin. Practical exploration demonstrates that this formation is a typical tight sandstone reservoir. Samples taken from the oil layer were divided into 6 diagenetic facies based on porosity, permeability and the diagenesis characteristics identified through thin section and scanning electron microscopy. To compare pore structure and their seepage property, a high pressure mercury intrusion experiments (HPMI), nuclear magnetic resonance (NMR), andwater-oil relative permeability test were performed on the three main facies developed in reservoir. The reservoir quality and seepage property are largely controlled by diagenesis. Intense compaction leads to a dominant loss of porosity in all sandstones, while different degrees of intensity of carbonate cementation and dissolution promote the differentiation of reservoir quality. The complex pore structure formed after diagenesis determines the seepage characteristics, while cementation of chlorite and illite reduce the effective pore radius, limit fluid mobility, and lead to a serious reduction of reservoir permeability.

scholarly journals Physical Simulation of Colayer Water Flooding in Low Permeability Carbonate Reservoir in Middle East

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Xingwang Shi ◽  
Zhengming Yang ◽  
Yapu Zhang ◽  
Guangya Zhu ◽  
Qianhua Xiao
Keyword(s):  
Middle East ◽  
Physical Simulation ◽  
Carbonate Reservoir ◽  
Water Flooding ◽  
Low Permeability ◽  
Pore Throat ◽  
Large Pore ◽  
Production Models ◽  
Small Pore ◽  
Comprehensive Recovery

To study the flow mechanism under different displacement modes of low permeability carbonate reservoir in the Middle East and to improve the utilization of various types of reservoirs, the physical simulation experiments of water flooding by different displacement methods were carried out. Selecting two types of rock samples with different permeability levels, two-layer coinjection and separated production experiments by samples I and III and conventional water flooding experiments by samples II and IV were carried out. In addition, by using low magnetic field nuclear magnetic resonance, the development effect of microscopic pore structure under the different injection-production models was analyzed. Results show that, compared with the coinjection, the recovery rate of sample I was higher than II, 19.30%; sample III was lower than IV, 23.22%; and the comprehensive recovery degree reduced by 3.92%. NMR data also show that the crude oil is mainly distributed in the large pore throat; after water flooding, the displacement is also within the large pore throat, whereas the small pore throat is mainly obtained by the effect of infiltration absorption. The above studies provide a laboratory basis and foundation for the further development of low permeability carbonate reservoir in different Middle East strata.

scholarly journals Pore Structure and Limit Pressure of Gas Slippage Effect in Tight Sandstone

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Lijun You ◽  
Kunlin Xue ◽  
Yili Kang ◽  
Yi Liao ◽  
Lie Kong
Keyword(s):  
Porous Media ◽  
Pore Structure ◽  
Gas Flow ◽  
Gas Permeability ◽  
Flow In Porous Media ◽  
Slip Effect ◽  
Tight Sandstone ◽  
The Core ◽  
Core Samples ◽  
Limit Pressure

Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment.

The Characteristics of Tight Gas Reservoirs Microscopic Pore Structure - To Sulige Gas Field as an Example

2015 ◽  
Vol 1092-1093 ◽  
pp. 1485-1489 ◽  
Author(s):  
Jun Sheng ◽  
Wei Sun ◽  
Ji Lei Qin ◽  
Shi Guo Liu ◽  
Ai Ju Li ◽  
...  
Keyword(s):  
Pore Structure ◽  
Physical Characteristics ◽  
Tight Gas ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Field ◽  
Tight Gas Reservoirs ◽  
Constant Rate ◽  
Sandstone Reservoir ◽  
The Impact

The research is based on conventional microscope experiments, the characteristics of microscopic pore structure of tight sandstone reservoir were analyzed via the constant-rate mercury experiment. This paper selected samples of tight sandstone are from the Southeast area of Erdos basin Sulige gas field. The results showed that the dissolution pore and the intergranular pore were mainly reservoir pore structure types; the bundle throat and the lamellar throat were mainly types of throat in the study area. The mainly configure relations of the pore and throat in this area were big pore - fine / fine throat. Finally, according to constant-rate mercury results, analyzed the impact of pore and throats for percolation capacity respectively, came to the conclusions that the tight sandstone gas reservoirs percolation capability in study area is mainly affected by the throat, and the development degree of the throat determines the final physical characteristics of the reservoir.

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