The underperforming production wells in many pilot research are commonly ascribed to two key contributing components: geological variation and completion strategy. Traditional statistical analysis and machine learning approaches have overlooked the integration of frac-hit and its impact on production performance due to the complexity and uncertainty. This paper carries out a careful study to compare well production performance by examining the frac-hits timing and severity in addition to differentiating the aforementioned component contributions via combined statistics, machine learning and game theory approach. Being able to analyze the two blocks in Luzhou shale gas reservoir using multiple benchmarks further identifies potential upside opportunities (eg.well spacing, completion schedule).
In this study, we utilize the tree-based machine learning model and the explicability tool Shapley Additive exPlanations (SHAP) with the key production indicators to distinguish the trend out of chaos. Specifically, the frac-hits timing and severity such as during which flow regime frac-hit occurred, the pressure increment and the duration are considered along with the completion and geological data. The proposed approach further enables fieldwide production forecast and to understand the additional impact of frac-hit timing and severity on top of the geo- and engineered-features. The application of the two blocks in Luzhou shale gas reservoir in Sichuan Basin showcases the significance and insight by incorporating frac-hits information to facilitate and optimize the asset portfolio.
A novel developed solution has been successfully applied to two shale gas blocks in Sichuan Basin to disentangle the complex interactions of increasing scale of completion design, changing geology, disparity of well spacing and the inclusion of the frac-hit event in particular. The results are mainly but not limited to: 1) the key drivers for well productivity in both blocks are identified and quantified in importance hierarchy (Eg. gas content, TOC, proppant intensity etc.); 2) casing deformation is a critical issue for both blocks that negatively influence the well performance; 3) wells experienced frac-hits at late time BDF with a controlled influencing duration leads to smaller damage to the productivity; 4) Higher pressure spike during frac-hits at linear flow most likely triggers a long-term loss of productivity.