scholarly journals Shale Gas Content Calculation of the Triassic Yanchang Formation in the Southeastern Ordos Basin, China

Energies ◽  
2017 ◽  
Vol 10 (12) ◽  
pp. 1949 ◽  
Author(s):  
Jiao Su ◽  
Yingchu Shen ◽  
Jin Hao ◽  
Bo Liu
Keyword(s):  
Shale Gas ◽  
Ordos Basin ◽  
Gas Content ◽  
Yanchang Formation

scholarly journals Shale Gas Content Calculation of the Triassic Yanchang Formation in the Southeastern Ordos Basin, China

2017 ◽  
Author(s):  
Jiao Su ◽  
Yingchu Shen ◽  
Bo Liu ◽  
Jin Hao
Keyword(s):  
Shale Gas ◽  
Calculation Method ◽  
Indirect Method ◽  
Ordos Basin ◽  
Gas Content ◽  
Dissolved Gas ◽  
Yanchang Formation ◽  
Free Gas ◽  
Shale Reservoirs ◽  
Method Show

Shale gas content is the key parameter for shale gas potential evaluation and favorable area prediction. Therefore, it is very important to determine shale gas content accurately. Generally, we use the USBM method for coal reservoirs to calculate gas content of shale reservoirs. However, shale reservoirs are different from coal reservoirs in depth, pressure, core collection, etc. This method would inevitably cause problems. In order to make the USBM method more suitable for shale reservoir, an improved USBM method is put forward on the basis of systematic analysis of core pressure history and temperature history during shale gas desorption. The improved USBM method modifies the calculation method of the lost time, and determines the temperature balance time of water heating. In addition, we give the calculation method of adsorption gas content and free gas content, especially the new method of calculating the oil dissolved gas content and water dissolved gas content which are easily neglected. We used the direct method (USBM and the improved USBM) and the indirect method (adsorption gas, free gas and dissolved gas) to calculate the shale gas content of 16 shale samples of the Triassic Yanchang Formation in the Southeastern Ordos Basin, China. The results of the improved USBM method show that the total shale gas content is high, with an average of 3.97 m3/t, and the lost shale gas content is the largest proportion with an average of 62%. The total shale gas content calculated by the improved USBM method is greater than that of the USBM method. The results of the indirect method show that the total shale gas content is large, with an average of 4.11 m3/t, and the adsorption shale gas content is the largest proportion with an average of 71%.  The oil dissolved shale gas content which should be taken attention accounts for about 7.8%. The relative error between the improved USBM method and indirect method is much smaller than that between USBM method and indirect method, which verifies the accuracy of the improved USBM method.

scholarly journals Gas Desorption of Low-Maturity Lacustrine Shales, Trassic Yanchang Formation, Ordos Basin, China

2018 ◽  
Vol 10 (1) ◽  
pp. 688-698 ◽  
Author(s):  
Bojiang Fan ◽  
Xiangzeng Wang ◽  
Liang Shi
Keyword(s):  
Shale Gas ◽  
Gas Adsorption ◽  
Ordos Basin ◽  
Isotopic Fractionation ◽  
Gas Content ◽  
Gas Generation ◽  
Desorption Process ◽  
Yanchang Formation ◽  
Gas Desorption ◽  
Process Gas

AbstractRecent exploration activities on Triassic Yan-chang Formation has indicated significant potential for shale-gas resources. Even though some areas have been put into pilot production, challenge exists in effectively determining shale-gas content, whichmake it difficult to estimate reserve and forecast production. This is primarily due to the low maturity of the shale and complicated relationships between oil, water and gas. However, studies on the gas generation and accumulation of low-maturity shales are lacking in the literature and previous desorption experiments did not consider the effects of oil and water. In this study, eight core samples are used to run the gas-desorption experiment. Shale-gas composition and isotopic fractionation data are analyzed to provide insights on gas adsorption, expulsion and accumulation processes in the Yanchang Formation. The experiment results indicate that the overall methane content decreases (from 68.8% to 58.9%), heavy hydrocarbon-gas content (from 20.30% to 36.12%) and δ13C1 increase (from -51.43% to - 34.63%) during the desorption process. Gas yield reached up to 3.89 m3/t shale, and the content of lost gas can account for more than 20% of total desorbed gas during the coring process. The recoverable shale gas content is estimated to be 80% of the total gas-desorption volume. Desorbing the rest 20% requires extra heating under much higher temperature.

Fractures in continental shale reservoirs: a case study of the Upper Triassic strata in the SE Ordos Basin, Central China

2015 ◽  
Vol 153 (4) ◽  
pp. 663-680 ◽  
Author(s):  
WENLONG DING ◽  
PENG DAI ◽  
DINGWEI ZHU ◽  
YEQIAN ZHANG ◽  
JIANHUA HE ◽  
...  
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Mineral Content ◽  
Ordos Basin ◽  
Total Content ◽  
Upper Triassic ◽  
Thin Sections ◽  
Yanchang Formation ◽  
Fracture Development ◽  
Shale Reservoirs

AbstractFractures are important for shale-gas reservoirs with low matrix porosity because they increase the effective reservoir space and migration pathways for shale gas, thus favouring an increased volume of free gas and the adsorption of gases in shale reservoirs, and they increase the specific surface area of gas-bearing shales which improves the adsorption capacity. We discuss the characteristics and dominant factors of fracture development in a continental organic matter-rich shale reservoir bed in the Yanchang Formation based on observations and descriptions of fracture systems in outcrops, drilling cores, cast-thin sections and polished sections of black shale from the Upper Triassic Yanchang Formation in the SE Ordos Basin; detailed characteristics and parameters of fractures; analyses and tests of corresponding fracture segment samples; and the identification of fracture segments with normal logging. The results indicate that the mineral composition of the continental organic-matter-rich shale in the Yanchang Formation is clearly characterized by a low brittle mineral content and high clay mineral content relative to marine shale in the United States and China and Mesozoic continental shale in other basins. The total content of brittle minerals, such as quartz and feldspar, is c. 41%, with quartz and feldspar accounting for 22% and 19% respectively, and mainly occurring as plagioclase with small amounts of carbonate rocks. The total content of clay minerals is high at up to 52%, and mainly occurs as a mixed layer of illite-smectite (I/S) which accounts for more than 58% of the total clay mineral content. The Upper Triassic Yanchang Formation developed two groups of fracture (joint) systems: a NW–SE-trending system and near-E–W-trending system. Multiple types of fractures are observed, and they are mainly horizontal bedding seams and low-dip-angle structural fractures. Micro-fractures are primarily observed in or along organic matter bands. Shale fractures were mainly formed during Late Jurassic – late Early Cretaceous time under superimposed stress caused by regional WNW–ESE-trending horizontal compressive stress and deep burial effects. The extent of fracture development was mainly influenced by multiple factors (tectonic factors and non-tectonic factors) such as the lithology, rock mechanical properties, organic matter abundance and brittle mineral composition and content. Specifically, higher sand content has been observed to correspond to more rapid lithological changes and more extensive fracture development. In addition, higher organic matter content has been observed to correspond to greater fracture development, and higher quartz, feldspar and mixed-layer I/S contents have been observed to correspond to more extensive micro-fracture development. These results are consistent with the measured mechanical properties of the shale and silty shale, the observations of fractures in cores and thin-sections from more than 20 shale-gas drilling wells, and the registered anomalies from gas logging.

scholarly journals Shale favorable area optimization in coal-bearing series: A case study from the Shanxi Formation in Northern Ordos Basin, China

2017 ◽  
Vol 36 (5) ◽  
pp. 1295-1309 ◽  
Author(s):  
Wei Guo ◽  
Weijun Shen ◽  
Shangwen Zhou ◽  
Huaqing Xue ◽  
Dexun Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Ordos Basin ◽  
Sedimentary Facies ◽  
Gas Content ◽  
Burial Depth ◽  
Organic Carbon Content ◽  
River Channels

Shales in the Well district of Yu 106 of the Shanxi Formation in the Eastern Ordos Basin is deposited in the swamp between delta plains, distributary river channels, natural levee, the far end of crevasse splay, and depression environments. According to organic geochemistry, reservoir physical property, gas bearing capacity, lithology experimental analysis, combined with the data of drilling, logging, testing and sedimentary facies, the reservoir conditions of shale gas and the distribution of an advantageous area in Shanxi Formation have been conducted. The results show that the total organic carbon content of the Shanxi Formation is relatively high, with an average content value of 5.28% in the segment 2 and 3.02% in segment 1, and the organic matter is mainly kerogen type II2 and III. The maturity of organic matter is high with 1.89% as the average value of Ro which indicates the superior condition for gas generation of this reservoir. The porosity of shales is 1.7% on average, and the average permeability is 0.0415 × 10−3 µm2. The cumulative thickness is relatively large, with an average of 75 m. Brittle mineral and clay content in shales are 49.9% and 50.1%, respectively, but the burial depth of shale is less than 3000 m. The testing gas content is relatively high (0.64 × 104 m3/d), which shows a great potential in commercial development. The total organic carbon of the segment 2 is higher than that of the segment 1, and it is also better than segment 1 in terms of gas content. Based on the thickness of shale and the distribution of sedimentary facies, it is predicted that the advantageous area of shale gas in the segment 2 is distributed in a striped zone along the northeast and the northsouth direction, which is controlled by the swamp microfacies between distributary river channels.

Origin of shale gas in the Triassic Yanchang Formation, Ordos Basin, China

2017 ◽  
Vol 35 (10) ◽  
pp. 969-974
Author(s):  
Qiang Meng ◽  
Xiaofeng Wang ◽  
Xiangzeng Wang ◽  
Peng Liu ◽  
Yuhong Lei ◽  
...  
Keyword(s):  
Shale Gas ◽  
Ordos Basin ◽  
Yanchang Formation

scholarly journals The Shale Gas Accumulation of the Triassic Yanchang Formation in the Ordos Basin, China

2015 ◽  
Vol 89 (s1) ◽  
pp. 281-281 ◽  
Author(s):  
Fengqin WANG ◽  
Zhili DU ◽  
Hongjun LIU ◽  
Linpei FAN ◽  
Shenbao BAI ◽  
...  
Keyword(s):  
Shale Gas ◽  
Ordos Basin ◽  
Yanchang Formation ◽  
Gas Accumulation ◽  
The Ordos Basin

Practical application of liquid-CO2/slick-water hybrid fracturing technology in the lacustrine shale gas reservoir in Ordos Basin, China

2015 ◽  
Vol 3 (2) ◽  
pp. SJ75-SJ80 ◽  
Author(s):  
Xiangzeng Wang
Keyword(s):  
Shale Gas ◽  
Ordos Basin ◽  
Volume Ratio ◽  
Shaanxi Province ◽  
Vertical Wells ◽  
Fracturing Fluid ◽  
Pumping Rate ◽  
Yanchang Formation ◽  
Well Production ◽  
Lacustrine Shale

The seventh member of the Yanchang Formation, Upper Triassic black shale deposited in the deep and semideep lacustrine environment, is located in the southeast area of the Ordos Basin. It is 1200–1800 m in buried depth and 30–60 m in thickness. As the main target of lacustrine shale gas in this region, the seventh member of the Yanchang Formation usually uses fracturing technology as the major stimulation treatment. Slick-water fracturing with a high-pumping rate has been successful early on, but the low reservoir pressure of this formation resulted in a large volume of fracturing fluid invasion. As a consequence, the shale-gas well production has been postponed owing to the low rate of fracturing-fluid flowback and a long cleanup period. Liquid-[Formula: see text] fracturing has caused almost no damage to the formation, and the volumetric expansion of [Formula: see text] after gasification will increase formation energy and improve the fluid cleanup rate. I have developed a liquid-CO2/slick-water hybrid fracturing technology that combined the advantages of liquid-[Formula: see text] and high-pumping-rate slick-water fracturing. Sixteen vertical wells and one horizontal well have been tested in the Ganquan Area, Shaanxi Province, China. As a result, the fluid cleanup rate improved 30% in comparison with regular slick-water fracturing. Moreover, the fracturing-fluid cleanup period of vertical wells decreased from 45 to 25 days. A field test indicated that because more liquid [Formula: see text] was used (i.e., the volume ratio of liquid [Formula: see text] to slick water increases), the performance of reservoir energizing and flowback result improved.

Identification and distribution of fractures in the Zhangjiatan shale of the Mesozoic Yanchang Formation in Ordos Basin

2017 ◽  
Vol 5 (2) ◽  
pp. SF167-SF176 ◽  
Author(s):  
Hui Shi ◽  
Xiaorong Luo ◽  
Hui Xu ◽  
Xiangzeng Wang ◽  
Lixia Zhang ◽  
...  
Keyword(s):  
Shale Gas ◽  
Seismic Waves ◽  
Ordos Basin ◽  
Super Resolution ◽  
Average Density ◽  
Gas Production ◽  
Small Scale ◽  
High Angle ◽  
Yanchang Formation ◽  
Angle Fractures

The natural fractures in mud or shale directly affect the quality and efficiency of shale gas reservoirs, and fracture identification and prediction play an important role in drilling shale gas wells and making plans for reservoir stimulation. We adopted ant tracking technology for 3D poststack reflective seismic waves to identify the size and distribution of high-angle structural fractures in the Zhangjiatan shale of the Yanchang Formation in the Ordos Basin, which is a typical continental shale. The parameters for ant tracking fractures are extracted from the investigation on outcrop, cores, and image logs. The prestack seismic diffractive wave imaging technique for the super-resolution identification of mid- and small-scale breakpoints can be used as the constraint conditions for ant tracking. The identified result of high-angle fractures was validated by the image logging and drilling gas logging results. The geologic and logging data indicate that the Zhangjiatan shale is mainly characterized by high-angle fractures and a smaller number of low-angle fractures. The fractures mainly trend in the near east–west direction, followed by the near north–south direction, and a small amount of fractures in the north–northeast and northwest–west directions. The average density of structural fractures is relatively low, but the cemented rate is only 15.7%, and most structural fractures maintain an open state. The identified and predicted structural fractures are mainly distributed in the southeast of well LP180 and south of well LP179. The higher gas shows from actual well drilling in shale directly correspond to the density and intensity of high-angle fractures rather than the matrix gas abundance in shale, which indicates that the sweet spot of gas production in shale is clearly controlled by structural fractures.

scholarly journals Influencing Factors and Mathematical Prediction of Shale Adsorbed Gas Content in the Upper Triassic Yanchang Formation in the Ordos Basin, China

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 265 ◽  
Author(s):  
Ling Tang ◽  
Yan Song ◽  
Zhenxue Jiang ◽  
Xiongqi Pang ◽  
Zhuo Li ◽  
...  
Keyword(s):  
Shale Gas ◽  
Influence Factors ◽  
Economic Benefits ◽  
Gas Content ◽  
Analysis Method ◽  
Isothermal Adsorption ◽  
Resource Potential ◽  
Yanchang Formation ◽  
Geological Factors ◽  
Factor Regression

Evaluating absorbed gas content (AGC) in shales is crucial for accurately characterizing shale gas reservoirs and calculating resource potential. To investigate geological factors influencing AGC, 15 shale samples collected from the Yanchang Formation underwent related experiments. Then geochemistry features, mineral compositions, pore structure parameters and external factors were analyzed. The actual AGC was calculated using the Langmuir equation. Single geological factors acting on the AGC were discussed by the single-factor correlation analysis. Finally, four main influence factors (total organic carbon, S1, quartz content and formation temperature) were selected out from the 12 influence factors to establish the mathematical prediction model through the multi-factor regression statistical analysis method using SPSS software. The model was verified as being reliable with R2 as high as 0.8046 and relative error less than ±20%. Comparisons show that both the CH4 isothermal adsorption experimental method and the multi-factor regression analysis method have their own applicability and disadvantages, and they can complement each other in evaluating AGC in shales. Synthetic evaluation of AGC indicates that the Yanchang shale has an overall moderate AGC occupying about 58% of the total, which is helpful to extend shale gas production time of the Yanchang reservoir. Though under the present conditions, economic benefits of the continental shale gas are not obvious, the shale resource potential of Yanchang formation can’t be ignored.

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