Abstract

Carbonate reservoirs, particularly those of Tertiary age, contribute significantly to South-East Asia's oil and gas production. There is considerable potential for more carbonate fields to be discovered in the future, because much of the region is still under-explored. Well logs recorded in these formations can, in many cases, be very difficult to interpret. Limestones and dolomites are hydrocarbon-bearing in Indonesia and the Philippines, as well as having good potential for hydrocarbon reservoirs around the fringes of the Indian and Australian land masses. Specific examples of recent well logging problems and their possible solutions are drawn from these areas.

The choice of optimum well logging suites, to maximize the amount of petrophysical information obtained from the carbonates, is discussed with petrophysical information obtained from the carbonates, is discussed with some of the new, as well as the traditional, interpretation techniques, used in many other areas of the world. Some recent advances in logging tool technology are featured, and a variety of interpretation techniques are shown to have good applications, particularly natural gamma ray spectroscopy and formation testing by wireline methods. Much of this advance has been in the last five years, in large part due to the advent of digital computer wellsite recording. Methods to identify fractures and permeability indication techniques are reviewed, as well as potential uses permeability indication techniques are reviewed, as well as potential uses of dip tools.

Introduction

Carbonate reservoirs, particularly those of Tertiary age, contribute significantly to South-East Asia's oil production. Many of these are reef structures which have grown only in shallow-water marine environments, with very little or no sediment input, and were extremely sensitive to water temperature and salinity. Platform carbonates are common off several of the area's continental margins, but no attempt is made to subdivide carbonate reservoirs for the purposes of this paper. Carbonate rocks, which require a carefully designed wireline logging programme and can be difficult to interpret, form important hydrocarbon reservoirs in Indonesia, the Philippines, and around the fringes of the Indian and Australian land masses. Specific examples of well logging problems are drawn from these areas. Figure 1 shows a profile across a typical carbonate shelf.

Logging programmes aimed at maximising the amount of petrophysical information obtained from the carbonates are discussed. Interpretation techniques are evaluated and some limitations of well logs in reef environments highlighted. Field examples from recent wells in South-East Asia are shown, and possible applications of new and future well logging tools proposed.

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