Classification and Evaluation on Shale Gas Reservoir for Wufeng-Longmaxi Formation in Chuannan Area, Sichuan Basin

Abstract

Based on the comprehensive statistic and analysis on some representative geological and physical data, the classification criteria on net pay for shale gas reservoir of the Wufeng-Longmaxi formation in Shunan area, Sichuan Basin, are proposed, which include porosity (φ), gas saturation (Sg), density of rock (DEN), brittleness index (BI), and gas content (Vt). When the porosity, gas saturation, brittleness index, and gas content are larger than 3%, 30%, 40%, and 1 m3/t, respectively, and the density of rock is lower than 2.7 g/cm3, then this formation can be seen as the net pay. The application of two key parameters, gas content and brittleness index, could reflect the reservoir resource basis and fracability, respectively. The gas content has a positive correlation with porosity and total organic volume, and the brittleness index has a positive correlation with siliceous and carbonate content. According to the range of these two parameters, the net pay can be classified into three types. For type I, the gas content and brittleness index are larger than 4 m3/t and 50%, respectively. For type II, either the gas content or the brittleness index is lower than 4 m3/t and 50%. For type III, the gas content should be larger than 1 m3/t and lower than 4 m3/t, and the brittleness index is between 40% and 50%. The field application case indicates that the Wufeng formation and low member of the Longmaxi formation have good quality and mainly consist of type I and II formations. In addition, it is found that there is a positive correlation between the penetration ratio for type I formation and the testing production and estimate ultimate recovery (EUR). While this ratio is larger than 50%, the testing production rate and EUR will be over 15×104 m3/d and 8000×104 m3 with a probability of 92%, which meet the requirement of exploitation with reasonable economic benefits.

Reservoir Characteristics and Exploration Potential Evaluation of Lower Cambrian Niutitang Shale in Northern Guizhou: A Case Study of Well QX1

“…Over the course of years, shale gas exploration and development have undergone significant advancements, there have been many successful commercial development of shale gas blocks and stratigraphic units both domestically and internationally [9,23,[39][40][41][42]. The basic param such as organic matter content, thermal evolution degree, kerogen type, brittle mineral content, pore type and shale thickness of the Niutitang Formation shale gas reservoir in QX1 well are compared with them (Table 3).…”

New insights into the evaluation criteria for high-quality deep marine shale gas reservoirs in the Longmaxi formation: Evidence from organic matter pore development characteristics

“…Currently, there are no specific unified criteria for the classification of shale reservoirs in China. In particular, the deep shale in southern Sichuan also uses middle-shallow reservoir classification criteria (Zhao et al, 2016;Guo et al, 2021). However, deep marine shale reservoirs are characterized by relatively low porosity and high gas content (Nie et al, 2022; Figure 14).…”

Correlation of Boreholes through Well Logs: Application to the Western Sector of Madrid

“…The use of well logs for borehole correlation and aquifer modelling has been used by several authors [ 18 , 19 ] with good results. Manual and automatic borehole correlation using well log segmentation has been used in many studies [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”