Abstract

In the rugged foothills of North Eastern BC are a number of river gorges that complicate conventional pipeline river crossings. This paper discusses the unique cementing requirements of Anadarko's Buckinghorse River Crossing completed in October 2004. The project involved drilling and connecting two horizontal wells on either side of the Buckinghorse River Valley. After being connected, the wells were used as a pipeline to tie in wells on one side of the river to the pipeline infrastructure on the other side of the river. Significant savings were realized using this technology compared to conventional pipeline technology. This project presented unique challenges, particularly cementing two horizontal casing strings at once with a reverse casing cement job.

Introduction

In the foothills of North Eastern British Columbia, many geographic barriers are present that inhibit both drilling and production operations. In the Buckinghorse area, Anadarko encountered a deep river valley that prevented the connection of a number of gas wells on one side of the gorge to production facilities on the other side. This gorge made conventional pipelining both uneconomical and environmentally challenging. Anadarko's successful completion of the Buckinghorse River Crossing provided a unique solution to the infrastructure barriers commonly encountered in developing gas properties in North Eastern British Columbia.

The river crossing design incorporated the drilling and intersection of two conventional horizontal wells on either side of the river valley. The surface location of the wells are located approximately 2.8km apart. Both wells have 339.7mm surface casing to approximately 240m and a 244.5mm intermediate casing string that is landed at approximately 90 ° (~ 1435 mTVD). A 222.2mm hole was drilled and intersected downhole at a true vertical depth of approximately 1435 m. One well was 2984m long and the second was 2792m long. Once connected, cased (177.8mm) and cemented, both wells acted as an approximately 6000m pipeline used to transport gas across the river valley without disturbing the natural beauty of the area.

This paper examines the unique challenges, associated with the cementing of two intersecting horizontal wells and how they were overcome during the execution of the river crossing program. After analysis and modeling, an annular cement job was successfully performed in which the production casing in both wells was cemented simultaneously. Details of the cement job design, simulation, and execution are presented. An overview of the river crossing design and discussion of other technical aspects of the drilling operations has been reserved for future papers.

Background

The Buckinghorse River Valley that separates Anadarko's existing Jedney production with the desired development areas of Green and Buckinghorse is a substantial geographical feature. With the river cutting approximately 300m into the surrounding landscape, slope stability issues exist on both the north and south river banks. In order for the well site locations to be stable, the wells needed to be situated approximately 2.8km apart. In addition to the issues of location stability, geological strata provided unique challenges of their own. The first directionally drillable formation is located at approximately 1430m true vertical depth.

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