Application of Silicate/Polymer Water Shutoff Treatment in Faulted Reservoirs with Extreme High Permeability

Lakatos, Istvan Janos (U. of Miskolc) | Lakatos-Szabo, Julianna (Research Institute of Appllied Earth Sciences, UM) | Kosztin, Bela (Petroleum Development of Oman) | Al-Sharji, Hamed Hamoud (Petroleum Development of Oman) | Ali, Ehtesham (Petroleum Development of Oman) | Al-Mujaini, Rahima Abdul Rauf (Petroleum Development of Oman) | Al-Alawi, Nasser (Petroleum Development of Oman)

OnePetro 

Abstract
In frame of the project, one injector and two oil producers operating in different reservoirs having extremely high permeability were treated using the silicate/polymer method. The well selection based on analysis of production history, reservoir structure, and tracer test and production characteristics. The water cut in producers was close to or well above 90%. The chemical system was individually tailored to each well. The gel-forming solutions were sequentially injected into the wells using bullhead technique. The producers operating with sucker rod pumping were treated through the producing tubing or the annulus. In the latter case, a new "virtual" reactor concept was elaborated to mix the solution on the fly. Evaluating the results, it can be concluded that the project was successful. The cumulative daily oil production increased by 68 m3/d; meanwhile the water production decreased by 285 m3/d. Thus, on yearly basis, the incremental oil production might be as high as ~25,000 m3/y with water production less than 105,000 m3/y. The project clearly proved that the silicate/polymer technology could meet the requirements of the unique reservoir conditions (extreme permeability, faulted structure, and low formation temperature). In addition, great advantage of the composite methods is that easily available, cheap, and environmental friendly chemicals were used.

Introduction
Background of arising problems in Omani hydrocarbon production can be traced back to unfavorable types of reservoirs and properties of oils. Most of the oil bearing formations are faulted, highly heterogeneous with extremely high average permeability. In addition, the formation temperature is often low and the crude oils have high viscosity. Hence, the early water breakthrough and high water cut are often characterizing the production. Under these circumstances, the recovery factor is low, and poor well performance usually jeopardizes the optimal oil rate. Recognizing and understanding the production problems and forecasting their detrimental effects on deliverability, substantial efforts had been made recently to avoid production decline and mitigate the damaging processes. Among others, IOR/EOR methods addressing the whole reservoir space and well stimulation technologies were tested and routinely applied at different fields. In the frame of these endeavors, ambitious pilot tests were carried out to restrict water production in oil wells and simultaneously, to improve sweep efficiency in injectors through flow profile control. Earlier, diverse techniques including cementing, perforation relocation, polymer, and gel treatment were tested with partial success. The basic goal of the extensive field programs was to select the most efficient methods, which are flexible enough to meet the requirements at different oil fields. That strategy made the field tests of the silicate/polymer methods possible treating two producers and one injector. The company's idea also determined the target wells operating in different oil fields, hence under different, sometimes harsh formation conditions.