Three-Dimensional High Efficiency Fracturing Technology for Preventing Casing Deformation in W Deep Shale Gas

Abstract

ABSTRACT The right of W mineral cover an area of 143.77km2. As shale gas horizontal wells are prone to casing deformation by segmental fracturing, the casing deformation rate exceeds 45%, which seriously affects the production capacity construction of shale gas wells in W block. A set of techniques for high-strength balanced fracturing process in multiple clusters for preventing casing deformation in W shale gas wells has been developed, including: 1) two evaluation indexes, namely stress-strain brittleness index and vertical stress and difference index between vertical stress and minimum horizontal stress, have been added to establish W deep shale fracturing quality evaluation index plate and realize fine division of segment clusters; 2) a multi-scale fracture network fracturing numerical model for W Shale gas wells was established for the first time via Eclipese software, and key fracture parameters such as optimal fracture half-length, flow conductivity and complexity were obtained; 3) in engineering construction, a multi-cluster, small particle size and variable displacement combination injection fracturing scheme has been proposed for two injection modes: planar perforation and spiral perforation, respectively, with the objective of reducing casing. INTRODUCTION Shale gas, as a new unconventional natural gas resource, occupies an increasingly important position in the energy sector. The economic development of deep shale gas in the US has gone through a process of continuous exploration and testing, improvement and refinement, with some blocks now meeting the requirements for economic development. Among them, 3 deep shale gas blocks in Haynesville, Eagle Ford and Canna Woodford with burial depths of 3500-4100m have been economically developed with single well gas production of more than 5×104m3/d after segmental fracturing of horizontal wells, with an average final gas recovery of more than 1×108m3 per well and an integrated cost of less than US$12 million per well (T.Lowe et al.,2014; Mauricio et al.,2013).