TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper details the challenges of stimulation in one of the fields in North Oman. The field is a mature, heavily faulted and fractured carbonate reservoir on water flood where acid stimulation carries an inherently high risk of inducing several fold increases in water production. Acid placement challenges are immense as the fracture networks impart massive permeability contrasts and are most often the principal conduits for "premature" injection water breakthrough. We present field data of acid stimulation treatments on cased hole, oil producers as well as open-hole horizontal injectors using a novel self-diverting acid system. This fluid has been recently applied in other reservoirs but to date, none of these applications have held the same magnitude of challenges and barriers to successful implementation of stimulation treatments. We present numerous field studies which identify self-diverting acid systems as a key solution, together with best practices in candidate selection (through reservoir logging evaluation) and coiled tubing placement methodology, in providing consistent improvement in net hydrocarbon well productivity and enhanced injection profile for reservoir management. In addition we present results of a new surfactant based self-diverting system and compare the results to conventional polymer based treatments in this field. The results are indicative of a further improvement in success ratio of acidizing treatments. Similar methodology and fluid systems are applicable in other complex fractured reservoirs where acid placement and minimizing water production present the principal challenges. Moreover, as reservoir management becomes an ever-increasing concern, we present a treatment methodology to enhance productivity, reduce water cut and optimise reservoir sweep, all of which reduce the overall lifting costs.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper describes new methods to economically improve production levels in one of the mature fields of Petroleum Development Oman. This field had been developed by infill drilling programs, which were suspended in early 2001 to review the development strategy. A reservoir management team set a challenge to effectively conduct logging operations and quickly utilize the data collected to identify and avail of optimization opportunities, thus maximizing the production of the wells whilst lowering overall costs. The optimization activity consisted of clean-out, saturation logging, perforation and stimulation. These activities were carried out either with coiled tubing only utilizing conventional practises and e-line coiled tubing, or with the combination of coiled tubing and hoist through multiple well entries. Both of these methods were successfull in that they resulted in incremental net oil production but at relatively high costs. This paper presents a methodology which enables clean-out, logging, stimulation and perforation with one coiled tubing intervention, which includes a plastic coated "e-line" coiled tubing, coiled tubing perforating head and new perforation technology. All systems are in complete compliance with the most stringent safety criteria. The new method has a considerable time and cost savings impact, and this is fully illustrated in this paper with field trial case histories, in which a multi-disciplinary team effectively targeted the most suitable zones for perforation and stimulation using a state of the art self diverting, non damaging, acid system. Technical and economic comparisons are made with conventional practices. The methodology is currently being employed in this field and is potentially applicable to other fields.