Schlumberger

Technical Paper: A Systematic Approach for Wellbore Drilling and Placement of SAGD Well Pairs and Infill Wells

Society: Other
Paper Number: WHOC11-503
Presentation Date: 2011
 

Abstract

The initial drilling of a set of Steam Assisted Gravity Drainage (SAGD) well pairs (producer and injector) from a pad for heavy oil development is often accomplished using standard well creation techniques for the initial wells (in our case the producers) followed by the careful drilling of the parallel wells using advanced ranging techniques to accurately control the separation of the paired wells. In this paper we first demonstrate an improvement in the SAGD service by taking a more holistic approach to this creation; emphasizing maximum accuracy in the well creation at every step and yielding improved final results. This process also should result in improvements in the further field development and assessment of reserves.

When drilling the initial well, it is of critical importance that the position of the well be accurately known. To do this, we analyze the surveys using advanced techniques such as multi-station analysis to yield the most accurate definition of the well path. Careful control of the directional drilling process is also critical. During large azimuth adjustments, it is important that the tortuosity of the well be minimized. Accurate control of the inclination (and thus TVD) is equally important during the lateral section. This is aided by at-bit determination of inclination. It should be noted that controlling as opposed to maintaining a uniform TVD may be required as the zone of interest may vary laterally.

Given this knowledge, the second well must also be carefully drilled and placed. Many of the above requirements are duplicated. During the build section, we often need to control azimuth in the presence of magnetic interference. This is accomplished using an alternate technique, Gravity MWDR, which allows the accurate determination of the well azimuth. In addition, using passive ranging allows the continuous determination of the location of the drilling well and to anticipate changes in drilling parameters needed to maintain the required relative position of the paired wells.

Drilling infill wells presents other challenges. These are often attempted several years after the initial development and the knowledge of the position of the existing wells is less sure. In such cases, we find that the wells are best drilled with careful analysis to detect magnetic interference. We thus ascertain that the drilling well correctly maintains the desired separation from existing wells in place.

This paper demonstrates the improvements in initial and subsequent field development due to applying a systematic approach when drilling and correctly placing heavy oils wells for SAGD development in Alberta, Canada.

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