Abstract

A number of tools are available for production improvements for wells where the cost of workover rigs cannot be justified or where workover rigs are unavailable. Recent literature has described some through tubing and rigless type workover innovations. This paper presents case histories explaining the use of production logging, coiled tubing, small bridge plugs, cement packers, acidizing and oriented perforating methods that resulted in excellent gas and oil production increases. Significant savings were experienced when compared to more conventional rig supported workovers.

Cement packers placed by coiled tubing and oriented through tubing perforating have been used in several cases to restore inactive wells to commercial production rates. This paper describes two such attempts. In another case, extraneous water production was identified with a production log and shut off with a simple bridge plug setting. This was followed by acid stimulation of the gravel pack to restore the damaged interval to good gas rates. A third case is also presented to show several problems that were encountered in an older well.

In order to select the appropriate technique and achieve the best results, a clear understanding of the problems, the objectives, and the available tools is needed for each case. This was accomplished by use of a multi-disciplinary team of various operating company and service company professionals involved in, the design and field operations to thoroughly review each proposal.

Introduction

VICO Indonesia operates several oil and gas fields in an area of East Kalimantan approximately 140 kilometers north of the city of Balikpapan (Fig. 1). These fields are operated under a production sharing contract with Pertamina, the Indonesian national oil company. VICO is the operator of a joint venture that began in the late 1960's and discovered commercial oil and gas in early 1972.

Today the production rates are approximately 1.7 billion cubic feet (Bcf) gas, 40,000 bbl of condensate and 30,000 bbl of oil per day from VICO's four major fields. Gas is transported and sold through the liquification (LNG) plant at Bontang, and the liquids are blended and sold via the tanker terminal at Santan.

Badak, the largest and oldest field, has now been completely developed by drilling. Because of the large number of reservoirs penetrated by wells in this field, workover operations will continue for many years to recomplete into shallower zones and repair existing completions.

Now, in efforts to maximize the use of all wellbores and considering cost containment issues, production engineers at VICO have designed and performed several unique work programs that utilize rigless methods at a cost of about one-third the cost of similar rig supported workovers. These programs involve the use of production logs, coiled tubing, special cementing techniques, oriented perforating, inflatable packers, acidizing cement packers, computer modelling, small diameter tools, etc.

Generally, very good success has resulted from the overall program. Gas production was increased by 130 million cubic feet per day (MMcf/D) and oil rates improved significantly in 1995. A few unexpected problems were encountered and these are also discussed.

TDT Log, Coiled Tubing cement Packer, Oriented Perforating - Badak Well number 121

The original completion for Badak well number 121 was a dual gas well. By 1993 both zones had watered out, but interest in a zone behind casing led to a thermal decay time (TDT) log survey (Fig. 2). This survey showed that the three zones in the B-12 reservoir were not uniformly depleted since the middle interval was wet while the upper and lower sections contained gas.

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