The Issaran field, a heavy oil reservoir with estimated original oil in place (OOIP) of approximately 1.6 billion bbl of oil, was discovered in 1981. The producing horizons are the carbonate formations of Miocene age occurring from depths of 1,000 to 2,000 ft. The oil is of 9 to 12 °API with viscosity of 4000 cP at standard conditions. It was not until early 2000, after the crude oil prices rose to favorable levels, that a concerted effort was made to develop this heavy oil. Cold production from the fractured carbonate Nukhul reservoir (depth approximately 2,000 ft) was first targeted and the production from the field increased from 170 barrels of oil per day (BOPD) in 1998 to more than 2,300 BOPD in 2002. However, the Upper Dolomite reservoir, at a depth of 1,000 ft, held more than 50% of the OOIP, but did not produce.
Subsequently, a pilot project using cyclic steam injection was implemented on two openhole completions in the Dolomite reservoir and the production results far exceeded predictions, proving it to be commercially viable. This pilot scheme was expanded to two, seven-spot pattern wells and the total combined production from the Issaran field reached 5,000 BOPD in late 2008. Recently, however, the productivity of the Upper Dolomite wells has declined. The water cut has increased and the steam injection efficiency is becoming questionable.
Because the steam temperatures of nearly 600°F exceed the operational limits of conventional production logging tools (PLTs), they cannot be used for steam injection profile monitoring. In addition, wellhead control and operational safety concerns become challenging issues. One effective solution to the problem was to run high temperature Memory PLT (MPLT). These tools are built for high temperature service and can be run on slickline, making this a more cost effective solution. The three wells selected for the preliminary run of the MPLT service were also the first applications of this technology in the Middle East area.
The primary results have already shown deficiencies in the steam injection process because most of the steam is being preferentially injected into water-bearing zones. This paper provides a detailed review of the results from the PLT surveys and the completion strategy implemented to improve productivity and maintain project profitability.