Evaluation of Bottom Hole Pressures in 40 Soft Rock Frac-Pack Completions in the Gulf of Mexico

Abstract

The purpose of this paper is to share findings that resulted from a study of pressures recorded from bundle carrier and wash pipe gauges run during frac-packing operations. The original premise was to correctly evaluate and identify fracture pressure responses associated with the "tip-screen-out" techniques used for frac-pack placement. The first attempts at frac pack pressure evaluation were done using data collected from bundle carriers in the workstring. Once washpipe data was obtained, it was noted that the bundle carrier data was distorted by phenomenon below the gauges in the well bore. The fluid friction generated through the crossover tool and friction associated with the slurry path around the screen proved to be a source of the observed distortion. Data collected from bottom hole pressure gauges attached to the wash pipe below the gravel pack running tool indicated that in several cases the observed pressure increase is associated with friction and not from the fracture inflation associated with "tip-screen-outs." It was noted that serious swabbing effects can accompany the movement of the service tool. This swabbing has in the past been considered negligible. The swab effect can potentially damage the completion beyond repair. This swab can pull formation material into the perforations tunnels and annulus, creating a severe pressure drop through that portion of the perforated interval. The implications can be detrimental to well performance. Early BHP data collection altered procedures for service tool movement and provided insight toward correcting friction pressure calculations.

Study on the Difference of Fracture Extension in Hydraulic Fracturing of Marine and Continental Shales Based on Optical Scanning Technology

“…Chong et al [29] first defined shale reservoir factorability as the nature of a shale's ability to be effectively fractured to increase production. Mullen and Enderlin [30] concluded that the factors affecting the compressibility of shale gas reservoirs mainly include sedimentary formations, stratigraphic properties, mineralogical composition and distribution, and the development of naturally weak surfaces. Geng et al [31] investigated the anisotropy of Longmaxi shale brittleness based on triaxial mechanical experiments and showed that the brittleness index is affected by the peripheral pressure and the angle of lamination.…”