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Development and Application of a Composite Silicate Gel for Water Shutoff Treatment in Hungary
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2019 – 20th European Symposium on Improved Oil Recovery, Apr 2019, Volume 2019, p.1 - 15
Abstract
Excess water production usually has negative influence on volumetric sweep efficiency, and as a result deteriorates the profitability of production operations. In the past half century, numerous techniques were extensively applied in frame of water shutoff technology including polymer-based macro- and microgels, emulsions, sols, crystalline compounds, etc. Surprisingly, the operators did not appreciated the use of silicates despite the fact that the silicates were proposed as chemical diverting agent and profile control already in 1922. In the past decades, the silicate technology has a revival because of their outstanding features, which is apparently superior to other gels. These facts are well proved by more than 100 well treatments carried out in Hungary, Serbia and Oman curing various problems including excess water production, water conning, leakoff, restriction of vertical gas migration in a collapsed well and profile control in water injection wells. Earlier, the pure silicate solutions were applied, however recognizing some weak points of the gel under HPHT conditions, substantial efforts were made to improve both the chemical systems and the injection protocol.
First, combining the silicates with polymers some fundamental deficiencies could be eliminated forming a double network in gel providing flexibility and much less sensitivity to fracture and syneresis at high-pressure gradient. Later, nanomaterials were added to silicate and silicate/polymer gels, which advanced nucleation providing faster, reliable and controllable gelation in case of sequential injection protocol. The detailed laboratory studies have shown that the gelation kinetics is also substantially modified because the polymer is a retardant, while the nanosilica is an accelerator influencing thus the setting time. In addition, inevitable advantages of the composite gel are that the technology is based on cheap, easily available, and environmentally friendly chemicals. The “green” method was first applied in an oil filed (Algyő 2, field, Hungary) already in 2014, and abundant information could be collected to summarize the results and lessons to learn. Application of silicate/polymer/nanosilica gel controlling the detrimental water production resulted in outstanding technical and economic results. In one-year basis, the water production decrease by 32,000 bbl, meanwhile the incremental oil production increased by 21,000 bbl. The net profit was 653,000 USD in contrast to the investment (OPEX) of 238,000 USD. Since the profitability of treatments was above the expectation, the operator plan to continue extending the advanced composite RCC method. The paper to be presented will give a detailed overview of the laboratory studies and pilot tests.