Horizontal well drilling is one of the technology currently used to exploit oil in reservoirs consisting low permeability zone, naturally fractured reservoirs, high cost-areas, and water coning zones (McCoy, 1996). Butun horizontal wells represent the usage of this technology to enhance oil recovery in a high cost area and water coning zones. The objective of this horizontal drilling program was to verify the existence of remaining oil reserves in the Butun field. If the remaining oil reserves in the field are sufficient then it would be exploited with two horizontal wells.
The accurate estimate position of the Oil Water contact (OWC) is one of the most critical factors in determining success of a horizontal well program. In Butun area there had been an uncertainty in the position of OWC, therefore a pilot hole was drilled to verify the CiWC position at the reservoir target. A decision analysis was developed to maximise the value of the project contains some uncertainties. It was shown by this analysis that drilling a pilot hole will optimise the value of the project. The OWC data at the reservoir target was used to determine how the drilling program would be proceeded. The decision to drill two, one, or not to drill any horizontal wells will be determined based on the oil thickness. The well will be deepened to the bottom of the Bekasap formation if the remaining oil reserves are insufficient.
This paper will address the steps in planning and executing the Project, as well as the results of drilling the directional pilot hole. Information gained from this project hopefully will help others to define appropriate screening criteria and provide guidance for planning a horizontal well in the water coning zones.
Authors : Tri Hananto & Bambang Wisnu Handono