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Old 05-15-2009, 07:25 PM
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Default Case Study: Teamwork, Planning and Experience Improve Drilling Performance and Result

Case Study: Teamwork, Planning and Experience Improve Drilling Performance and Results during Horizontal Well Construction
Overview
Based on 1999 Schlumberger reservoir optimization studies, SIBNEFT and its subsidiary, SIBNEFT Noyabrskneftegaz, launched a four-well horizontal-drilling pilot project in western Siberia. The project was an important element in the SIBNEFT plan to raise crude output from 17.2 million tons in 2000 to 22 million tons in 2002.

Reservoir modeling indicated that perwell cost should be held to $1.2 million to make the project cost-effective. Actual cost averaged $1.5 million per well, but greaterthan- expected production more than compensated for this overrun. Despite time and cost overruns, the pilot project validated the SIBNEFT strategy of using new technology to improve production and reinforced its determination to continue that strategy.

The next four wells, which were very similar to those in the pilot project, benefited greatly from experience gained on the pilot project wells. Costs for the second four wells averaged $1.3 million, largely owing to a decrease in nonproductive time (NPT). Production from three of the wells exceeded expectations by about 60%, and production from the fourth well, Yarainer 611, was more than 500% greater than anticipated.

Time and costs for wells in progress are running 10% to 15% less than on the second four wells. The most recent well, Sugmut 2251, has been drilled and completed in only 54 days, considerably less than half the time taken to complete the first Sugmut well. Learning from experience, coupled with good teamwork and thorough planning, has been instrumental in this success.

Technical description
The pilot project well-construction team was formed in January 2000. Its members were a SIBNEFT Noyabrskneftegaz drilling manager, who acted as project chairman, a Noyabrskneftegaz drilling engineer and two Schlumberger project management drilling engineers.

There were four wells in the pilot project-one in the Yarainer field, two in the Romanov field and one in the Sugmut field. They targeted reservoirs at 2700 to 2850 m total vertical depth and had horizontal drain lengths of 500 to 600 m.

To meet the cost targets that reservoir modeling had indicated were needed to make the wells cost-effective, the team had to maximize use of existing SIBNEFT resources in the area. The challenges included communication-managed by translators and bilingual drilling engineers introduction of new casing sizes in a culture that had valued standardization use of conventional Russian rigs with standard capabilities-approximately 200-ton hoisting capacity integration of western European technologies and equipment such as the ARC Array Resistivity Compensated tool for logging while drilling combining Russian directional drilling practice with western European horizontal well design-use of nonrotating aluminum drillpipe, common in Russia, made drilling directional profiles more challenging extremely cold weather- temperatures of -35C to -45C.

The first horizontal well in the pilot project, Yarainer 608, was spudded in July 2000 and the last, Sugmut 2301, was completed in March 2001. NPT for the wells averaged 48%-a major reason why costs were higher than planned. Production rates exceeded expectations on all wells except Yarainer 608, which encountered unexpected reservoir conditions.

Because a different rig had drilled each well and none of the rig crews had previous horizontal-drilling experience, the well-construction team believed performance would improve significantly and NPT would decrease as experience was gained. SIBNEFT Noyabrskneftegaz, convinced that its strategy of introducing cost-effective new technology to improve production was correct, approved the drilling of eight more horizontal wells using the equipment and personnel from the pilot project.

Costs for the first six wells in Phase 2 were lower than on the pilot project; NPT was reduced 75% and production expectations were exceeded. Based on these results, SIBNEFT Noyabrskneftegaz approved the drilling of an additional 42 slimhole horizontal wells in 2002. In addition, 2000- and 3000-hp rigs will be used to drill larger, higher-displacement horizontal wells.
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