Abstract

Atlantic Richfield Indonesia, Inc. (ARII) recently drilled a well with a 1500-foot horizontal leg in a ten foot thick poorly consolidated sand. This paper describes the planning and drilling of this well, focusing on the use of real-time geosteering technology to maximize well placement in the pay zone. Additional topics include drilling fluid design to ensure borehole stability while minimizing formation damage, and the role of rock strength analysis from cores in designing the open hole completion. A narrative of the drilling and completion of the well is given, along with the initial production history.

Introduction

The 'B' field is located approximately 60 miles northeast of Jakarta, Indonesia in ARII's Offshore Northwest Java Sea (ONWJ) contract area (Fig. 1). It is a north-south trending structure with bounding faults to the east and west. Production in the field is from a number of structurally flat, thin, marine shelf sands (Fig. 2). In 1994, a multi-disciplinary team (MDT) was formed to review development opportunities in the B field. One of the areas of focus was the BM platform, which had already been planned and approved. Of primary concern was the potential for water encroachment through the platform drainage area as a result of production to the south. A 3D seismic survey and reservoir simulations were used to study if water could have moved through the BM platform area (Ref. 1).

Mapping from the 3D survey resulted in a substantial loss of reserves in the 29A1 and A2 main sandstone targets. However, a new 3D structure map for the 28C reservoir, and a better understanding of the original oil-water contact from capillary pressure core studies, placed significantly more oil in the 28C reservoir to the northeast of BM platform. This was confirmed by history matching from reservoir simulations. Unfortunately, by this time the platform had been set. To recover the 28C reserves to the northeast of the platform, the subject well of this case history, BM-3, was proposed.

Planning

Over 24,000 feet of horizontal hole has been drilled in ARII's ONWJ contract area, primarily in the 'ZU' area of the Bima field between 1986 and 1988. These horizontal wells targeted the Batu Raja limestone formation and utilized long radius directional drilling technology to place an 8-1/2" wellbore in a 40-50 foot thick oil column (Ref. 2). The wells were navigated along pre-determined trajectories with directional surveys. Geologic feedback into the drilling loop was limited to cuttings, shows and penetration rate analysis, but a relatively firm cap rock provided a good ceiling marker.

Planning efforts for the BM-3 horizontal well were centered on two major issues:

  1. methods of placing, monitoring and controlling the position of the well in the pay zone; and

  2. providing borehole stability throughout the life of the well.

Geometric versus Geologic Steering. The operational challenges associated with successfully placing a lateral well in a pay zone can be divided into two parts:

  1. "landing" the well, i.e. getting the hole horizontal at the correct depth, attitude and displacement; and

  2. keeping the well in the zone.

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