In deep, south Texas fields, water production is an issue that continues to hinder mature fields and significantly impact operating costs and production performance. These wells are slimhole monobore completions with 2 7/8- or 3 1/2-in. tubing cemented in place. This small restricted inside diameter (ID) limited the available methods of shutting off water in slimhole monobore commingled wells.
In the past, the operator would perforate, fracture treat, and flow test each zone separately. Because of this completion practice (long cycle times) along with a shortage of personnel, equipment, and the cost of materials and services, the company has changed its completion strategy. In an attempt to reduce cycle time and cost, a new, more-effective completion strategy was developed, in which the operating company adopted a continuous operation plan to complete all zones (perforate and fracture treat) of interest and then commingle the production on completion of the fracture treatments in the well. Although this next-generation completion strategy or technique was more efficient, it required additional diagnostics to determine which zones were producing water and if the water-to-gas ratio was hindering the well’s performance.
An organically crosslinked polymer (OCP) was successfully placed into the wells, eliminating or greatly reducing excess water production. Although the reservoir parameters were not in the high-pressure/high-temperature (HP/HT) range, the water shutoff required particular attention. Using this technology, the operator reduced water production and disposal costs and increased gas production in some instances.
This paper presents guidelines for completing successful water shutoff based on case histories from the operator’s field. It describes diagnostic methods used, aspects of the required design criteria, operational concerns, and required quality assurance/quality control (QA/QC) testing. Pre and post-treatment water results are also presented.