Review Of Early Horizontal Well Applications In Central Sumatra

Abstract

C.W. Arnold* and H. H. Djauhari* Abstract This paper reviews the first applications of horizontal wells in the Caltex Pacific Indonesia (CPI) area of operation in Central Sumatra, Indonesia. Drilled in late 1993 and early 1994, these wells now provide enough history for an initial evaluation of the results. These results are encouraging and CPI is reviewing further applications of this technology, which is viewed as another technique for squeezing more oil out of mature fields. The project histories, ranging from concept to evaluation, drilling, and actual performance results, are briefly covered. Emphasis is placed on the evaluation methodology, involving a blend of analytical and simulation methods, and comparison of performance predictions with actual results. Introduction CPI's area of operation is characterized by numerous mature fields with significant reserves, permeability, aquifer influx, and multiple stacked sandstone reservoirs. High producing water cuts and water coning are significant problems. Both the Minas and Petani fields used horizontal wells to target thick bottomwater sands which cone significantly in vertical wells. In Minas, the objective was to reduce water cut and capture bypassed oil from a fining upward section. In Petani, the concept was to reduce coning, increase rates, and improve well management by allowing the recompletion of existing vertical wells upward into unopened pay. The evaluations included a review of the geology and performance predictions designed to address the complications in each field. These include the very high permeabilities and fining upward sequence in Minas and the influence of neighboring wells in Petani. Generally, the results have been good and these projects offer useful case histories of horizontal well applications. Background Both the Minas and Petani fields are located in the Pertamina-CPI Production Sharing Contract Area in Central Sumatra, Indonesia (Fig. 1). The Minas field is the largest in Southeast Asia with an estimated original-oil-in-place (OOIP) of nine billion barrels. The Petani field, although smaller, is still sizeable with an estimated OOIP of about 690 million barrels. Petani is located 12 miles west of the Duri field, site of a large steamflood operation. Significant oil reserves remain in both fields and methods of efficiently recovering that oil are of strategic interest to the company. P. 337