Production Data Analysis of Shale Oil Reservoir Using the Dynamic Drainage Pore Volume Concept: Lessons-Learned from Well-To-Well Fracture Driven Interaction in Lucaogou Shale Formation

Abstract

Many pilot researches consider production gains or losses in parent/child wells in short-term thereby determining the optimal completion parameters (eg. well spacing, stage spacing). Long-term recovery varies from negative-to-positive during the post-frac-hit evaluation based on the magnitude of the pressure sink and the distance of parent/child wells. However, quantitatively analyzing frac-hits impact remains unsolved. This paper presents a novel workflow combining RTA diagnostic plots and the prediction of dynamic drainage pore volume (DDPV) to analyze the frequent well/well fracture-driven interaction (FDI) (commonly referred to as frac-hits) in the Lucaogou shale formation, Junggar Basin. According to the published knowledge, different strategies have been employed in Lucaogou formation to minimize the negative effect and to avoid the parent/child wells (e.g cube-development). Thus, optimizing stage, cluster and well spacing in well-pad zipper-frac development is in necessity. This paper first reviews the frac-hit mechanisms in both parent/child wells and well-pad zipper-frac development. We then characterize, quantify and rank the historical frac-hit events in Lucaogou formation based on the documented data. With the prediction of DDPV using numerical integration/differentiation assisted by diagnostic plots and specialized plots in RTA (eg. flowing material balance plot, square-root-of-time diagnostic plot), the pressure sink front can be acquired. The accuracy of DDPV forecast is validated using a synthetic case study. We further apply it to three field case studies to demonstrate the versatility and applicability of the proposed workflow. The successful applications suggest that the proposed workflow is an alternative to making field-development decisions, minimizing the negative impacts of frac-hits and thus freeing the cashflows. The outcomes are mainly but not limited to: 1) the common early departures from linear flow regime are in good alignment with the DDPV forecasts in both parent/child and well-pad development scenarios; 2) A competition of the per-well DDPV might be triggered during frac-hits in parent/child well and 3) long-term recovery in well-pad development with a tighter well-spacing might be boosted with a smaller per-well DDPV and DOI.