scholarly journals Analysis of Microscopic Main Controlling Factors for Occurrence of Movable Fluid in Tight Sandstone Gas Reservoirs Based on Improved Grey Correlation Theory

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xuefei Lu ◽  
Fengjuan Dong ◽  
Xiaolong Wei ◽  
PengTao Wang ◽  
Na Liu ◽  
...  
Keyword(s):  
Physical Properties ◽  
Physical Property ◽  
Type I ◽  
Type Ii ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Gas Field ◽  
Correlation Theory ◽  
Gray Correlation

Tight sandstone reservoirs have the characteristics of poor physical properties, fine pore throats, and strong microheterogeneity compared with conventional reservoirs, which results in complicated movable fluid occurrence laws and difficult mining. Taking the tight sandstone gas reservoir of He 8 formation in Sulige gas field as an example, based on physical property test analysis, constant velocity mercury injection, and nuclear magnetic resonance experiments, an optimized gray correlation calculation model is established by improved gray correlation theory, which quantitatively characterizes the influence of microscopic pore structure parameters of different types of tight sandstone gas reservoirs on the occurrence of movable fluids, and the main controlling microgeological factors for the occurrence of movable fluid in tight sandstone gas reservoirs with close/similar physical properties are selected. The results show that the occurrence of movable fluid in Type I reservoirs is mainly affected by the effective pore-throat radius ratio, the saturation of mercury in the total throat, and the effective pore radius, and the occurrence of movable fluid in Type II reservoirs is mainly affected by the effective throat radius per unit volume and total throat mercury saturation and mainstream throat radius. Moreover, the occurrence state of movable fluids in Type II reservoirs is controlled by the throat radius stronger than that of Type I reservoirs. It has important guiding significance for the efficient development of tight sandstone gas reservoirs.

scholarly journals Multifractal Characteristics and Classification of Tight Sandstone Reservoirs: A Case Study from the Triassic Yanchang Formation, Ordos Basin, China

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2242 ◽  
Author(s):  
Zhihao Jiang ◽  
Zhiqiang Mao ◽  
Yujiang Shi ◽  
Daxing Wang
Keyword(s):  
Pore Structure ◽  
Ordos Basin ◽  
Type I ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Yanchang Formation ◽  
Porosity And Permeability ◽  
Sandstone Reservoir ◽  
And Migration ◽  
Mercury Injection Capillary Pressure

Pore structure determines the ability of fluid storage and migration in rocks, expressed as porosity and permeability in the macroscopic aspects, and the pore throat radius in the microcosmic aspects. However, complex pore structure and strong heterogeneity make the accurate description of the tight sandstone reservoir of the Triassic Yanchang Formation, Ordos Basin, China still a problem. In this paper, mercury injection capillary pressure (MICP) parameters were applied to characterize the heterogeneity of pore structure, and three types of pore structure were divided, from high to low quality and defined as Type I, Type II and Type III, separately. Then, the multifractal analysis based on the MICP data was conducted to investigate the heterogeneity of the tight sandstone reservoir. The relationships among physical properties, MICP parameters and a series of multifractal parameters have been detailed analyzed. The results showed that four multifractal parameters, singularity exponent parameter (αmin), generalized dimension parameter (Dmax), information dimension (D1), and correlation dimension (D2) were in good correlations with the porosity and permeability, which can well characterize the pore structure and reservoir heterogeneity of the study area, while the others didn’t respond well. Meanwhile, there also were good relationships between these multifractal and MICP parameters.

scholarly journals The Effect of Multi-Scale Faults and Fractures on Oil Enrichment and Production in Tight Sandstone Reservoirs: A Case Study in the Southwestern Ordos Basin, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Lianbo Zeng ◽  
Wenya Lyu ◽  
Yunzhao Zhang ◽  
Guoping Liu ◽  
Shaoqun Dong
Keyword(s):  
Large Scale ◽  
Ordos Basin ◽  
Oil Production ◽  
Small Scale ◽  
Type I ◽  
Type Ii ◽  
Tight Sandstone ◽  
Micro Scale ◽  
Multi Scale

The Chang 8 Member of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin is a typical tight sandstone reservoir and has an average porosity of 8.60% and air permeability 0.20 mD. Multi-scale faults and fractures are widely developed in these reservoirs. In this study, three-dimensional seismic data, outcrops, cores, imaging logs, and thin sections were used to classify faults and fractures at multiple scales. Combined with the oil production data, the influence of multi-scale faults and fractures on the oil enrichment and production was analyzed. The results show multi-scale faults and fractures can be divided into six levels: type-I faults, type-II faults, large-scale fractures, mesoscale fractures, small-scale fractures, and micro-scale fractures. As the scale decreases, the number of fractures increases in a power function. Type-I faults cut the caprocks and are not conducive to the preservation of oil. Type-II faults connect the source rocks and reservoirs and are migration channels of the oil source. Large-scale fractures cut the mudstone interlayer and are the seepage channel inside the reservoir. Mesoscale fractures are controlled by thick interlayers, and small-scale fractures are restricted by thin interlayers or layer interfaces. These fractures are the main seepage channels and effective storage spaces. Micro-scale fractures serve as important storage spaces for these reservoirs. The case study of oil reservoir development proves that type-I faults have the greatest impact on fluid flow, while wells drilled into the type-II faults zone have a higher oil production capacity. The oil production changes with the development degree of fractures in different scales, strikes, and positions of faults. Meso- and small-scale fractures are the key to influencing the early single-well production, and micro-scale fractures are conducive to the stable production of single wells. Consequently, multi-scale faults and fractures have significantly different effects on the oil enrichment and production of tight sandstone reservoirs, and the research conclusions can guide to the exploration and development of such similar reservoirs.

scholarly journals Impact assessment of interlayers on geological storage of carbon dioxide in Songliao Basin

2019 ◽  
Vol 74 ◽  
pp. 85 ◽  
Author(s):  
Deping Zhang ◽  
Chengkai Fan ◽  
Dongqin Kuang
Keyword(s):  
Physical Properties ◽  
Songliao Basin ◽  
Type I ◽  
Type Ii ◽  
Geological Storage ◽  
Storage Efficiency ◽  
Reservoir Prediction ◽  
Injection Volume ◽  
Sand Body ◽  
Cap Rock

Reservoirs in the Songliao Basin are characterized by strong heterogeneity, which increases the difficulty of exact reservoir prediction. The clay interlayer developed in the reservoir is an important factor affecting the heterogeneity of the reservoir. Using the reservoir numerical simulation technology, an attempt has been made to investigate the storage efficiency during CO2 sequestration in Songliao Basin considering different types of interlayer in underground formations. Results indicate that type I interlayer, with a large thickness embedded between the two sand bodies has function of shunting and blocking to alleviate the impacts on cap rock. The type II interlayer has a small thickness and locates inside a single sand body, with poor physical properties and continuity, which has the same blocking effect on CO2 distribution and moderating influence on the cap rock. The physical properties of type III interlayer are same as the type II interlayer, but it has uneven distribution and poor continuity. In addition, three schemes of perforated zone were designed and their effects on CO2 storage efficiency and stability were studied. For a single reservoir, the scheme I is to perforate a whole reservoir, which is more conducive to maintain the reservoir’s stability. For multiple sets of “single-reservoir”, the scheme II can be preferentially selected to perforate the reservoir section below the interlayer when the injection volume is small. However, the scheme III can be used to perforate the interlayer and the reservoir below that when the injection volume is large. The study is beneficial to provide guidance and advice for selecting a suitable CO2 geological storage and reduce the risk of CO2 leakage.

Engineering-oriented “sweet spot” prediction for tight sandstone gas reservoirs: A case study from Sulige gas field in Western China

2020 ◽  
Vol 8 (4) ◽  
pp. T813-T821
Author(s):  
Hailiang Li ◽  
Liping Zhang ◽  
Jinyong Gui ◽  
Hailong Wang ◽  
Shengjun Li
Keyword(s):  
Hydraulic Fracturing ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Western China ◽  
Brittleness Index ◽  
Petrophysical Properties ◽  
Sweet Spot ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Field

Tight sandstone gas reservoirs have the characteristics of low porosity and permeability, deep burial, and low production of vertical wells, which are difficult to predict and exploit. Usually, finding a “sweet spot” requires finding zones with well-developed fractures or easy stimulation by hydraulic fracturing in the later stage. For some tight sandstone gas reservoirs where natural fractures are not developed, directional hydraulic fracturing is a good choice to improve single well production. However, not all reservoirs can achieve the desired productivity after hydraulic-fracture stimulation. In the exploration of the Sulige (SLG) gas field in Western China, sweet spots with strong brittleness and good petrophysical properties can ensure the success of hydraulic fracturing. We have evaluated the SLG gas field to determine how to implement an engineering-oriented sweet spot prediction workflow. The method has five steps: data-quality analysis, lithology prediction, brittleness prediction, petrophysical property prediction, and well planning. We evaluated the feasibility of subsequent sensitive elastic parameter inversion by comparing the accrual and simulated seismic gathers. Then, we used a direct inversion method of Young’s modulus to predict lithology and identify fluid at the same time. Next, we constructed a new brittleness index by combining the rate of change of Young’s modulus and the quartz content to evaluate the brittleness of rocks, which can overcome the shortage of the conventional brittleness index constructed by a single parameter. Finally, by using the brittleness index, we combined the petrophysical properties inversion results to select regions with strong brittleness and good petrophysical properties as the basis of well planning. This workflow achieved remarkable results in the exploration of tight sandstone gas reservoirs in the SLG gas field in Western China.

scholarly journals Structural studies on the microfibrillar proteins of wool. Interaction between α-helical segments and reassembly of a four-chain structure

1983 ◽  
Vol 209 (3) ◽  
pp. 587-595 ◽  
Author(s):  
L C Gruen ◽  
E F Woods
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Chain Complex ◽  
Alpha Helix ◽  
Chain Structure ◽  
Urea Solution ◽  
Type I ◽  
Type Ii ◽  
Difference Spectra ◽  
Alpha Keratin

The alpha-helix-rich particle of Mr 50 200, derived by limited alpha-chymotryptic digestion of the solubilized microfibrillar proteins from wool alpha-keratin, consists mainly of polypeptide-chain segments of Mr 12 500 (fraction ChC) and 25 000 (fraction ChB). The 12 500-Mr segments are of two types (I and II), which are derived from different polypeptide chains of the microfibrillar complex. Each of these type-I and type-II segments partially self-associates in benign solvents to form either dimers or tetramers. When mixed, the two segments show changes in physical properties (alpha-helix content, difference spectra and molecular weight) indicative of complex-formation. The maximum changes occur when the two segments are mixed in an equimolar ratio. Complexes isolated after rapid dialysis of mixtures from 8 M-urea solution were examined by various methods. A tetrameric structure is the main product formed in all cases, and the maximum amount of tetramer is obtained from equimolar mixtures of the type-I and type-II polypeptides. When urea is removed by dialysis from the unfractionated 12 500-Mr segments (fraction ChC) or from the alpha-helix-rich particle itself, a similar complex of Mr 50 000 is formed. The physical properties of these reconstituted entities (alpha-helix content, molecular weight, thermal stability and exposure of tyrosine residues) are similar to those of the original alpha-helix-rich particle. Cross-linking experiments with dimethyl suberimidate are in agreement with a four-chain complex for the reassembled structures. A pair of double-stranded alpha-helices is proposed for the particle, and is considered to be an integral part of the microfibrillar complex in wool alpha-keratin.

A New Method to Predict Favorable Gas-Rich Area in Tight Sandstone Gas Reservoir in Daniudi Area

2013 ◽  
Vol 295-298 ◽  
pp. 3328-3332
Author(s):  
Hai Ying Han ◽  
Zhi Zhang Wang ◽  
Xin Xiao Sun ◽  
Wei Jun Wang
Keyword(s):  
Ordos Basin ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Gas Field ◽  
High Productivity ◽  
Integrated Method ◽  
Geological Information ◽  
Sedimentary Microfacies ◽  
Developing Area

Daniudi gas field is a tight sandstone gas field in the northeast of Ordos Basin. How to use the successful experience in developing area to predict favorable gas-rich area in other areas in this gas field is very important to the next exploration and development in this field. This paper proposes a multi-information integrated method to predict favorable gas-rich area. Firstly describe sedimentary microfacies by integrating seismic, logging and geological information; and then summarize and analyze the seismic reflection patterns of medium-high productivity wells; finally determine the favorable gas-rich area with the distribution of storage coefficient based on the previous analysis. The welltest of newly drilled wells shows that the coincidence rate of favorable gas-rich area predicted by this method could be up to 90%,and this method could be extended to use in the other tight sandstone gas reservoirs.

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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