Significant breakthroughs have been made in the exploration and development of deep marine shale gas within the Luzhou Block of southern Sichuan Basin, China. Researchers recently conducted extensive studies focusing on the factors influencing gas content and sought to establish quantitative prediction models to facilitate the exploration of this valuable resource.
Deep marine shale gas is primarily found within the Longmaxi Formation, where production rates from different wells exhibit considerable variability. For example, during formation testing, Well Weirong WY23-1 achieved impressive gas production rates of approximately 2.6 × 105 m3/day, significantly contrasting with lower outputs from other wells, such as Well Yang 101H88-1, which peaked at only 7 × 104 m3/day. Such discrepancies underline the complexity and variability of gas content within these formations, which demand thorough investigation and modeling.
The importance of this study lies not only in its exploration of gas contents but also its exploration of the main variables affecting said contents. Utilizing various high-level analysis techniques, researchers conducted vitrinite reflectance analysis, kerogen microscopy, TOC content analysis, and gas content measurements, among others. These sophisticated methods shed light on factors such as organic matter types, mineral composition, pressure, and temperature conditions affecting the gas content.
Vital findings reveal the nuanced relationship between gas content and various geological factors. For adsorbed gas, parameters such as total organic carbon (TOC) content, clay minerals, and formation attributes like temperature and pressure were found to be significant influencers. Specifically, researchers noted, "the content of adsorbed gas is mainly affected by Ro, TOC content, porosity, water saturation, clay mineral content, formation temperature and pressure." Conversely, the study indicated the free gas content is primarily governed by porosity, water saturation, formation temperature, and pressure. Data showed clear correlations, with adsorbed gas quantity exhibiting positive relationships with both TOC and porosity.
On developing predictive models, the authors employed traditional statistical methods, including the Langmuir equation and multiple regression analysis, to assess correlations among the impacting factors. By synthesizing these relationships, they established quantitative prediction models demonstrating how adsorbed gas content could be effectively estimated under varying conditions. According to their findings, when TOC increases, the maximum adsorbed gas content proportionally rises, with the models providing detailed predictions across varied shale intervals within the Luzhou Block.
Overall, the research effectively established predictive models for both adsorbed and free gas contents, indicating substantial correlations with well production. Notably, "the higher the predicted gas content of a well is, the higher the EUR of the well is," underscoring the invaluable insights gained for future exploration efforts. The study classified the gas zones across the region, with well-defined areas ranking based on total gas contents, setting the stage for targeted extraction efforts.
While significant strides have been achieved, the research also hints at future directions for exploration, emphasizing the necessity for continual adaptation of predictive tools to account for varying geological variables. The established models are instrumental for guiding both the extraction and optimization of deep marine shale gas, paving the way for sustainable energy solutions moving forward.