Horizontal well construction/completion process in a Gulf of Mexico unconsolidated sand: development of baseline correlations for improved drill-in fluid cleanup practices

Abstract

This thesis examines, in detail, the procedures and practices undertaken in the drilling and completion phases of a Gulf of Mexico horizontal well in an unconsolidated sand. In particular, this thesis presents a detailed case history analysis of well planning, completion and cleanup operations. Our objectives are to present a complete examination of the openhole horizontal well construction/completion process using a new drill-in fluid (DIF). Further, we will establish data critical to development of new cleanup correlation techniques (the continuing goal of the CEA-73 industry consortium). Project results are intended to advance the technology progression of cleanup in horizontal welts by using a "Best Completion Practices'' well to establish a baseline analysis for development of rigsite DIF cleanup correlations. Presented in this thesis are: * Completion specifics of subject well * Audit of horizontal well design/well construction process * Documentation (on-location) of lignite practices * Laboratory analyses of DO cleanup * Well performance analysis Well audit results show that prudent DIF selection requires a thorough understanding of formation and reservoir specifics, along with completion and cleanup operations. Adequate pre-planning by lignite personnel for handling, weather problems, storage/mixing requirements and fluid property maintenance are very important for successful operations using DIF. Proper maintenance of solids control systems is essential for quality control of DIF properties. Detailed well planning by the operator (Vastar Resources), coupled with a conscientious mud service company (TBC-Brinadd, Houston), led to smooth execution of well completion/cleanup operations.aboratory analyses of field DIF samples taken during drilling show that entrained drill solids in DIF can greatly impact mudcaps removal during cleanup. However, well performance was roughly three times original expectations, achieving a stabilized gas flow rate of approximately 34 MMCF/D. Horizontal well decline type curve techniques and a proprietary analysis method developed by Conoco were used to estimate formation properties, using only wellhead production rates and pressures. Using these results, we estimated DIF cupcake removal for various reservoir permeability scenarios. Results suggest that a high percentage of DIF filtercake removal was achieved only if reservoir permeability was less than the permeability range (100-500 md) initially estimated by the operator.