Frac-Packing Previously Gravel-Packed Well Offers Alternative to Expensive Sidetracking
Authors: Feder Judy 
Published: September 2019

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 191001, “Fracture Packing in Previously Gravel-Packed Well Using Single-Trip Multizone System,” by Jianming Deng, Yingwen Ma, and Ming Zhang, China National Offshore Company; Jiacheng Qian and Chao Fang, Halliburton; and Qiang Wang and Xiaobo Wang, formerly Halliburton, prepared for the 2018 IADC/SPE Asia Pacific Drilling Technology Conference, Bangkok, Thailand, 27–29 August. The paper has not been peer reviewed.

This paper details the design and execution of what the authors say they believe is the first successful frac-pack operation in a previously gravel-packed well. The well, in China’s Bohai Bay, exemplifies a new method of recompleting mature wells to enhance production without performing a sidetrack, thus significantly reducing costs. Challenges and solutions are discussed as well as the methods used to squeeze fluid and proppant into the formation.

Introduction

For the past 13 years, a single-trip multizone (STMZ) gravel-packing system has been widely used in Bohai Bay for sand control. The practice has been to run single-trip, multizone, wire-wrapped screen in the casing and then perform a gravel pack for each stage. In some wells, production can decline quickly and the well can stop flowing within a couple of years. A typical solution is to pull the upper completion, plug the lower completion, and sidetrack. The cost of this method can be significant. Operators desired a lower-cost workover plan that would restore production from the current completion. The proposed method involved recompleting a well by running in service tools to perform fracture packing within the existing multizone gravel-pack completion. High-viscosity fluid would be pumped into the formation as a prepad; then, fracture packing would be performed.

The reservoir of the Suizhong 36-1 field in the Liaodong Bay area of the Bohai Sea is composed of multilayer sandstone formations. This field experiences sand-production issues for several reasons.

Because of its high permeability and high porosity, the formation sand is unconsolidated.

Production began in 1993, and, over the years, water has been injected to maintain it. Currently, the average water cut is 70%. Water production can cause sand production.

The oil is heavy. It has a high asphaltene content, and its viscosity is 37–160 cp, which generates significantly high friction forces when flowing in the near-wellbore region, thus increasing the likelihood of sand production.

The treatment includes cleaning the wellbore for recompletion. Use of the STMZ system proved the downhole service tool could be tripped back in and out of hole safely in the same trip following fracture packing of a previously gravel-packed multizone well completion. The method also shows that, through careful planning and designing of the tool and treatment, the risk of failure caused by a stuck tool string, unwanted fluid loss, or premature screen out can be minimized. The job execution and lessons learned also can provide a guideline for improvement of future treatments in similar situations.