Abstract

The 70's have seen carbonate reservoirs become important in Indonesia. New logging and interpretation techniques have conjointly been developed.

The Dual-Laterolog (DLL)* simultaneously records a deep and a shallow laterolog and a Micro-Spherically Focused Log (MICROSFL)* which measures the resistivity of the flushed zone. This combination allows good determination of the true formation resistivity hence water saturation in cases where the Induction log reaches its limitations.

The Dual-Spacing Compensated Neutron Log (CNL)* combined with the Compensated Density Log (FDC)* allows easy differentiation between oil and gas in relatively clean reservoirs. Shaliness sometime render the interpretation less straightforward and deep invasion combined with high gas movability can make it very difficult indeed.

In carbonate reservoirs, the detection of dolomitized zones is important because of their usually higher porosity and permeability. The FDC-CNL is useful in that respect and CORIBAND* computation gives the percentage of dolomite after corrections for hydrocarbons and clay content. Also, CORIBAND allows indentification of the transition zone and prevent costly mistakes in perforating zones with initial water-cut.

The 4-arm High Resolution Dipmeter (HDT)* has progressively replaced the 3-arm dipmeter. Its excellent resolution when combined with adequate software extends the field of dipmeter applications, one of which is the study of environment at the time of deposition in terms of prevailing energy. This in turn is used as a help to well-to-well correlation.