Petroleum Development Oman (PDO) has some 30 active fields in the North of Oman which produce from both Carbonates and Clastics. About a third of all wells in the North are horizontal and/or multilateral of various vintages with a large variety of completion environments i.e. barefoot, perforated cased hole, Elastomer Zonal Isolation Packer (EZIP) completions and Electric Submersible Pump (ESP) wells. Historically, down-hole flow patterns encountered in these wells have been very difficult to measure and interpret. Therefore, it was intended to use the most comprehensive suit of logs to determine real time three phase flow entries along the well bore. Only when all three phases are quantified is it possible to have confidence in appropriate well work-overs, interventions and/or increase reservoir understanding. The logging aimed to improve production optimization and proper well and reservoir management. This paper intends to review the advance production logging jobs performed in a year period from 2006 to 2007, from several fields in the North of Oman. The paper includes the following:
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Pre-job planning, recommended logging procedures, operational planning and considerations for different type of wells, well completion strategy, etc.
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Factors influencing horizontal production logging jobs
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Evaluation, log quality control and interpretation results
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Optimization of success rate through candidate selection and best practices
A summary of all the advance production logging job objectives and results will be shown. The main learnings per field and completion type along with way forward recommendations will also be summarized.
PDO commenced drilling horizontal wells in the North of Oman back in the 80's. Since then, most development projects used a high proportion of horizontal and multilateral wells to access reserves.
Historically, downhole inflow patterns encountered in these horizontal wells have always been challenging to measure and interpret. The usual challenges of horizontal production logging are described in another paper, "Production Logging Low Flow Rate Wells with High Water Cut1".
Recently, the FlowScan Imager (FSI*) was identified as a viable production logging tool to increase our understanding of real time three phase flow with an aim to assist in production optimization and proper well and reservoir management. This paper will review and analyze a number of FSI* logging jobs conducted in the fields of North Oman.
With any well related operation it is important to discuss the success rate of obtaining data. Figure 1 shows the FSI* jobs' success rate in producing oil Fields of North Oman. The traffic light colors indicates whether the job was successful (green) or not (red). "Technical success" (amber) is based on whether the logging objectives set prior to the job were met or not. In some cases, well work-over entries were performed based on the findings from the FSI* job and some production gains have been recorded. However, this paper does not intend to analyse the work over entry gains versus cost.
The high success rate (13 successful FSI* logging jobs out of the 18) was partially due to proper candidate selection, but most of all due to proper planning (Success with 3 out of 6 in Field 1, 5 out of 6 in Field 2, 3 out of 3 in Field 3 and in Field 4, 2 out of 3). Of the remaining 5 unsuccessful jobs, 2 were due to tool failures which were not re-attempted and 3 where either failure to log the entire interval of interest or could not be logged due to operational constraints giving poor quality data.
