Microchannel Remediation of a Cement Packer Unlocks Mature-Field Potential
Authors: Carpenter Chris 
Published: December 2018

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 189350, “Unlocking the Economic Potential of a Mature Field Through Rigless Remediation of Microchannels in a Cement Packer Using Epoxy Resin and Ultrafine Cement Technology To Access New Oil Reserves,” by Manu Khanna, SPE, Phanijyoti Sarma, SPE, Krishna Chandak, SPE, and Apurv Agarwal, SPE, Cairn Oil and Gas, a vertical of Vedanta, and Animesh Kumar and James Gillies, SPE, Halliburton, prepared for the 2018 SPE/IADC Middle East Drilling Technology Conference and Exhibition, Abu Dhabi, 29–31 January. The paper has not been peer reviewed.

Well RXY is located in Cairn’s Ravva offshore field in the Krishna-Godavari Basin in India. One goal for the field was significant crude production by means of a secondary reservoir section. This paper presents a case study concerning rigless remediation of microchannels in the cement packer (placed in the annulus of production tubing and casing to isolate the producing zone) and discusses laboratory development of a customized epoxy-resin system, simulations to estimate channel size, 3D displacement modeling, drillout after placement, and evaluation post-placement.

Introduction

The well is an injector, drilled in 1998, intersecting several oil sands. The well was completed selectively across the sands with permanent packers for zonal isolation. Although several oil sands were intersected during drilling, one was not completed because of its marginal reserves. Because those sands fall above the production packer, a cement-packer job was attempted in 2016 to access the shallow sands while providing an annular barrier. However, after the job, communication was observed between the tubing and the annulus. The communication was attributed to poor cement isolation.

Estimation of Channel Size

Fluid-flow calculations and a hydraulic simulator were used to estimate the size of channels in the cement. The calculations were based on the real data of treated-water circulation. The circulation was established between the production tubing and the A annulus through holes punched at 2282 to 2284 m. For calculation purposes, the top of cement was assumed to be 1500 m (per the cement-bond log) and the average channel size from a depth of 2282 m to a depth of 1500 m was to be estimated. Also, the actual well directional data were used for the most-accurate hydraulics calculations.

After several iterations, the channel size was estimated to be 0.3875 in. in average thickness.

Selection Criteria

Various techniques were evaluated to remediate the issue of channeling and to restore zonal isolation. Because the scenario was identified as one involving a narrow cement channel to be treated by the pressure-balance method, a proprietary epoxy-resin system was selected as the sealant. The selection was made on the basis of the sealant’s ability to seal the microannuli behind the casing and to restore zonal isolation by shutting off the gas flow, its characteristics in developing high compressive strength, its ability to resist significant strain without failure, and its solids-free formulation.