This paper will detail how a mature oil field in the South Kalimantan region of Indonesia was revitalised by the use of hydraulic fracturing. The Tanjung Raya field is a complex, multilayered, mature oil field. This field was initially developed in the 1960's, with production peaking at over 55,000 bopd. By the mid 1990's, production had declined to less than 1,200 bopd. The introduction of a water flood increased production to a peak of 10,000 bopd, but this quickly declined at an average rate of circa 33% per year. With the introduction of a fracturing programme, based on treating existing and new wells, production has been maintained at a flat 7,000 bopd over the past two years. The hydraulic fracturing program has accounted for 80% of these significant production gains, adding more than 5.7 million barrels of recoverable reserves and extending the economic life of the field by more than 2.5 years.
Hydraulic fracturing is a process that is relatively underutilised in the Asia-Pacific region, as compared to North America, Latin America and the Middle East. With a couple of recent noticeable exceptions, the technique is either not considered during field development and redevelopment, or it is used on a one-off, remedial basis. However, fracturing can be an integral part of well design, and an effective tool when the technique is applied systematically by practitioners who understand its capabilities; as demonstrated in the Tanjung Raya field.
This paper will discuss how a significant increase in oil productivity from a mature field was attained with a very high propped fracture treatment success rate. It will also detail how the correct design of fracture treatments can enhance reservoir recovery rates, and fully utilise vertical wells as a low cost, effective alternative to horizontal wells, or to increase well spacing. The paper will also discuss the most significant issues of implementing such a program and how these issues were effectively dealt with in the Tanjung field.
Introduction
Description of Field
The Tanjung structure is located in the northeastern Barito basin in the Southeast corner of Kalimantan (Indonesian Borneo), as illustrated in Figure 1.
The structure is a large, NS to NNE-SSW oriented, asymmetric faulted anticline, bounded on the west and north by a high-angle major thrust-fault with about 1500m of throw. The approximate dimension of the Tanjung structure is 9 km long and 3 km wide. The field covers an area of about 4000 acres. The Tanjung structure is a very late stage Plio-Pleistocene and is originally a normally faulted structural low, with a thick development of Tanjung formation. During the late Miocene and Pliocene, the Barito basin was subjected to a major phase of compression, thrust faulting, anticlinal folding, and strike slip faulting. This tectonic activity created most of the present day structures in the Barito basin, including Tanjung (see Appendix 1 for structural maps, Figures 8, 9 and 10).
