Abstract

Today, horizontal well technology is the viable option for draining complex geological reservoirs. Geological modeling allows proper placement of the wells, especially in thin reservoir targets, complicated by spatial stratigraphy variation and structural complexity. The model is generally constructed by integrating exploration and production well data, and seismic data to get more equitable flow unit distributions, and bedding dip, within existing reservoir structures. The 3-D modeling procedures used in this study involve deterministic and stochastic methodologies. Deterministic modeling used weighted-average data while stochastic modeling used a series of random processes, which statistically describes the relative probability of all data within the search radius as a function of distance. Stochastic modeling is used to access reservoir heterogeneity, especially when data is sparsely available. The modeling procedures were illustrated with three case studies: Indonesia Northeast Betara, California Giant Wilmington Field, and North Sea Andrew Field. The case studies highlighted the following:

  • It is almost impossible to access the reservoir horizontally without building a 3-D geological model of the reservoir.

  • A good 3-D geological modeling has a great benefit to access a complex structural and stratigraphic reservoir and in the area having a surface elevation problem.

  • Expensive surface location area can be overcome by efficiently placing selected/ limited surface pad locations to cluster the horizontal wells.

  • Modeling requires multi-disciplinary team work of specialists, which allows more efficient work flow, quick adapted decision and update, enhance quality control, and significant cost saving.

Introduction

Most recently, horizontal well drillings in a complex geological reservoir are done and tested digitally in 3-D geological and simulation modeling in order to place the well in a correct best reservoir unit and fluid targets in the subsurface. In a very complex geological area it is extremely difficult to place the well without having 3-D reservoir-geological modeling. The challenge to developing the reservoir is where horizontal drilling required in a thin reservoir target, is complicated by spatial stratigraphy variation and structural complexity.

3-D geological modeling improves reservoir understanding easily and, as an important tool for multi-expertise communication, provides a better presentation and visualization of reservoir architecture and fluid behaviors. The model is generally constructed by integrating exploration and production well data, and seismic data to get more equitable flow unit distributions and bedding dip, within existing reservoir structures that facilitate the placing of the horizontal well at the best ideal target possible. In the mean time, team work of multidisciplinary approach allows more efficient work flow, quick adapted decision and update, enhance quality control and significant cost savings.

All available data are integrated to build a 3-D reservoirgeological modeling. From vertical well data, production, pressure data, to the out-crop analog data that are used to develop depositional model, characterize reservoir architecture, reservoir facies trend and geometry, and its properties distribution. This integrated interpreted model is used to select the best horizontal targets possible. During the drilling of the well, the model can be interactively reviewed to further steer the real-time well direction in to more precisely desired flow units.

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