Best Practices for Sustained Well Productivity: A Lookback in to Deepwater Frac-Pack Completions

Abstract

Long term productivity is impacted by both the magnitude and rate of skin growth during the life of the well. Many deepwater Gulf of Mexico (GOM) Operators experience premature Productivity Index (PI) decline, which significantly impairs the economics of many major capital projects (MCP). Stringent application of best practices in both design and execution phases of deepwater wells can alleviate premature skin growth during the well life. The current study summarizes some critical best practices that impact the rate of PI decline in a broad dataset of recent cased hole frac pack (CHFP) completions. This study outlines a methodology to assess the relative impact of numerous variables that affect the frac pack deliverability. Application of this methodology requires early project phase development of a 3D mechanical earth model optimizing the number and location of drill centers and associated well paths ensuring they are optimal for frac pack completions. The methodology includes the completion phase, and that the assessment of completion-execution performance is fed back into the planning of future wells. This feedback loop across deepwater projects identifies best practices in execution and continual improvement in future completions. Over 70 CHFP completions in six different deepwater fields are assessed and correlated to their productivity trends. Information from this broad dataset helps to develop new and confirm established best practices. These best practices are derived by cross-functional analysis of factors related to the reservoir, completion-design, execution and the effects on long term deliverability of these wells. Our analysis concluded that three specific factors showed the highest impact in achieving a successful CHFP with improved initial skins and anticipated lower rate of skin-increase with reservoir pressure decline. While many sub-factors contribute to their relative impact, these three key factors include: 1) fracture- wellbore connectivity; 2) sufficient fracture-width and conductivity in the near-wellbore region to withstand changing reservoir conditions; and 3) an undamaged and intact annular proppant pack. The details associated with improving the likelihood of achieving each of the key factors and other findings are explored in-depth in the current work. Consideration of these high-impact variables and other best practices is-assessed and quantified within the new workflow, providing feedback to improve future completions and MCP developments. Our data set provides the most comprehensive collective study of frac pack completions in the Gulf of Mexico. Furthermore, the cross-functional expertise that contributed to the analyses of sub-variables brought the "best minds to the table". These attributes and the wide number of variables that were examined outline key best practices that should apply to any CHFP execution. The improved completions- workflow and comparison between producing CHFP completions allow prediction of future productivity trends. Possession of this knowledge enhances the predictability of production forecasting for business planning purposes.