Innovative Spinner Design Aids in Flow Characterization and Production Optimization of a Multistage Frac Well

Abstract

An operator working in Indian western land reservoirs, planned to develop a low-permeability, high potential reservoir with hydraulic fracturing. In the pilot project, production behavior of the initial wells was below expectation. As a diagnostic procedure few of the wells were attempted with memory coiled tubing-assisted production logging to record production log data and identify the root cause behind poor performance. Apart from the horizontal trajectory, major challenges associated with this approach included the low flow rate (150-200bbl) and expectation of frac fluid inside the wellbore due to inadequate cleaning. As a result, all the attempts for effective diagnosis were inconclusive. Moreover, absence of critical input such as individual stage frac evaluation demanded attention in order to optimize completion quality (CQ) and conclude effective fracturing and completion strategy prior to full field development planning. Addressing the challenges and with an aim to provide the critical inputs required for reservoir characterization and production optimization, a multi-spinner production logging tool with new innovative spinner design and multi-electrical and optical sensors were proposed on cased-hole tractor in order to resolve the complex flow profiles associated with the low flow rates and horizontal well trajectory. The newly configured spinners with innovative spinner design material lowered the spinner threshold from 2ft/min to 1ft/min for multipass logging in lab tests. It also optimized the magnetic field distribution to ensure less accretion of debris on the spinner (causing spinners to clog) without compromising measurement accuracy. With well production being 200 bbl at the time of logging, the multi-spinner survey with innovative spinner design clearly resolved the dynamic changes across the borehole during multi bean data acquisition. Overcoming the major interpretation challenge of isolating the dynamic changes in the wellbore due to borehole trajectory and due to fracturing stage, individual stage frac flow contributions were evaluated. Stage frac productivity correlated very well with the frac operation parameters, reservoir quality and completion quality. Apart from individual contributions, key findings such as activation of few frac stages at high drawdown pressures, increasing gas contribution from toe to heel and resolving presence of leftover frac fluid in the well, exceeded the expectations set by the client in terms of the objectives vs. results. This success clearly demonstrated that knowledge of downhole dynamics for horizontal trajectory is vital. This is not limited only to address the individual well requirement, but an integrated approach would help to optimize future wells through better understanding of reservoir productivity vs frac operation and completion quality (CQ).