This paper discusses a rigid-setting-fluid (RSF) system that has proved successful for curing severe dynamic and static losses, pumping treatments through the drillstring bottomhole assembly (BHA) (no trip out required), because of its highly controllable fast-setting properties. In addition to drilling applications, this system has also been used to shut off undesired fluid production during offshore workover interventions in extreme cases where conventional cement slurries or polymer-gel systems have yielded little success.

Introduction

Excessive water production from hydrocarbon-producing wells is one of the more serious problems in the oil industry. Water tends to become the dominant produced fluid as hydrocarbon fields mature. Unwanted water production can affect well economics adversely because of water-disposal costs, environmental issues, and reduced hydrocarbon production. Other problems can develop as a result of the undesired water production, including sand production, scale, and corrosion. Water-production problems assume various forms: leaks in casing, producing tubing, or packers; flow behind casing; water coning (or water cresting in horizontal wells); or direct communication from the injector to the producer through high-permeability streaks or natural or induced fractures. Several techniques for controlling water production have been attempted, including mechanical and chemical treatments or combinations of both. This paper describes an innovative temperature-activated RSF system used for water and gas shutoff in near-wellbore (NWB) applications.

Another problem discussed in this paper is severe lost circulation while drilling. Uncontrolled losses to the formation represent a high-cost event during drilling stages, especially in offshore environments. These losses can be classified according to their severity: loss of circulation by filtration (1 to 10 bbl/hr), partial loss (10 to 500 bbl/hr), and total loss (500 bbl/hr or greater). Conventional lost-circulation materials (LCMs) used to control losses include bridging agents, gelling agents, or cementing-type materials. Most of the time, ­cementing-type materials are left as the final option because they require pulling the drillpipe out of hole and running with a cement stinger, resulting in significant additional cost to the drilling stage. On the contrary, even though most of the bridging and gelling LCMs can be pumped through the BHA, most of the time, they are not suited for high-rate losses. While the discussed RSF was originally developed for conformance applications, its chemical and mechanical properties provide a unique solution for treating severe cases of lost circulation—in particular, those related to natural or induced fractures—while pumping the treatment through the BHA.