Abstract

This paper briefly discusses the abnormally high temperature and pressure conditions in the Arun Gas Field and examines the special mud requirements caused by these extreme conditions.

The next section focuses on the Liquid Mud Plant (LMP) which has been developed for use in the Arun Field to meet these special drilling fluid requirements.

The paper's conclusion points out the particular benefits of the LMP which produce cost savings in terms of both time and materials. produce cost savings in terms of both time and materials

Introduction

A Liquid Mud Plant (LMP) has been developed in the Arun field since the first Arun development well was drilled in 1976. The Liquid Mud Plant was built for mixing, treating and storing expensive invert oil emulsion mud. The economic need to conserve and reuse this mud was realized early in the development phase of the Arun field. The invert oil emulsion mud is mainly used in the drilling of Arun wells below the 13-3/8" intermediate casing where abnormally high temperatures and high pressures are encountered. A diagram and explanation of the physical layout of this LMP is given in Figures 1 and 1A. Figure 2 shows the average static reservoir pressure and temperature curves for Arun wells.

The Need For Invert Oil Emulsion Mud

In the discovery and delineation drilling phase, wells were drilled using a lignosulfonate type mud to depths which varied from 11000' to 12000'. Most drilling problems were associated with the high temperature and high pressure shale and salt water sands which overlie the high pressure of the pressure shale and salt water sands which overlie the high pressure of the Arun limestone gas reservoir. In the last two delineation wells, an invert oil emulsion mud was used to drill through the Lower Keutapang, Baong and Arun formations. The Keutapang and Baong shales are also water sensitive. It was found through experience that the invert oil emulsion mud performed better than a lignosulfonate type mud. It required less treatment and eliminated many of the problems in drilling the lower Keutapang, Baong and Arun formations. As a result of this experience, invert oil emulsion mud is used in Arun development drilling when the well penetrates these formations.

The Need For Two Types Of Invert Oil Emulsion Mud

Two types of invert oil emulsion mud are used in the Arun wells.

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