Abstract

The Belida Field, which is located in Block 'B' PSC area, South Natuna Sea, has been developed with thirty one development wells and six exploratory wells. The average water depth is 250 feet. Two separate reservoirs encountered in the field are the Lower Arang and the Udang sandstones.

Most of the development wells are highly deviated (40 to 70 degrees) and conventional logs ('Supercombo' DLL-MSFL-GR-SP-LDT-CNL-DT) were used to evaluate the reservoirs. However, in the high angle wells, drillpipe assisted logging tools were required, substantially increasing the cost of the logging program. To reduce the evaluation costs, a Logging While Drilling (LWD) suite was used. The LWD tools were run initially in BB-03, a 53 degree angle well which was being drilled adjacent to an abandoned exploration well Alu Alu E-5.

A comparison between the LWD logs and the conventional wireline logs indicated the LWD tools adequately evaluated the pay zones and saved considerable rigtime. A total of nine wells were evaluated with both conventional wireline (drillpipe assisted) and LWD tools. The LWD results were favourable.

LWD resistivities read higher than those obtained by conventional logs in the pay zones of the Lower Arang Formation. The difference in resistivity measurements between conventional and LWD logs will be investigated further in this paper. No significant difference was observed in the Udang pay zones.