Identification Of Reservoir Compartments Research Articles

Application and implication of horizontal well geochemistry

This paper describes the application of horizontal well geochemistry for the first time. Closely spaced samples, taken along a horizontal or deviated well path, allow the identification of reservoir compartments. Significant variations in geochemical parameters are related to the field filling and, if they persist over geological time and over tens of metres, should reflect barriers to diffusion and, by inference, possibly also to fluid flow. Two different approaches have been chosen: (a) closely spaced head space gas samples; (b) wet cuttings-based techniques. Case studies are presented documenting the detection of sealing faults between different reservoir compartments at the time of sampling. This novel approach has several advantages: (i) the need for costly pressure measurements is reduced; (ii) high sample density allows better spacial definition of barriers compared to both seismic and pressure measurements; (iii) detection of sub-seismic barriers; (iv) it allows detection of compartments even in cases where no pressure differences exist; (v) the technique works in wells drilled with oil-based mud systems. The strong variations in the geochemical signal over short distances has implications for the filling of reservoirs. The data suggest that reservoir filling is far more complex than previously envisaged.

APPLICATION OF RESERVOIR GEOCHEMISTRY IN THE IAGIFU-HEDINIA FIELD, PAPUA NEW GUINEA

In oilfield development and appraisal, a variety of tools are used to help define future reservoir performance. The identification of reservoir compartments, whether vertical or lateral, is a critical part of this evaluation. Reservoir compartments may develop over geologic or production timeframes depending on the characteristics of the reservoir seals. Frequently, the identification of some reservoir compartments is made only after the field is put on production.Reservoir pressure data is commonly used to identify reservoir compartments. A powerful complement to the pressure data are the properties of the reservoir fluids themselves. This provides a direct measure of hydrocarbon continuity. Both physical properties, such as gravity, bubble point pressure and GOR, and molecular properties of the oil are used. The detailed hydrocarbon composition of the reservoir fluids can be determined by a number of geochemical methods. In this paper we use capillary gas chromatography to generate oil fingerprints based on the molecular composition. We show how the oil fingerprint data is a sensitive discriminator of reservoir compartments.Reservoir studies of the Iagifu-Hedinia Field, Papua New Guinea, show the benefit of using a combination of geochemical, geological and engineering data. Each type of data reflects a different characteristic of the reservoir compartments. The combination of oil fingerprint and RFT pressure data demonstrated that some seals have been effective over geologic timeframes while others are effective only on a production timeframe. Geochemical data have also indicated the presence of reservoir compartments where other data were missing or inconclusive. Subsequently acquired production history data have confirmed the geochemically-based interpretations.