Abstract
The majority of the reservoirs in a study field in Indonesia are gas producers with water. The average production is more than 650 MMscf/D with 11,000 BWPD. The reservoirs are characterized as multilayered sandstone water-sensitive formations with permeability ranging from 0.1 md to 2 darcy. The measured depths (MD) of the perforated producing zones extend from 9,400 to 11,100 ft, with an average reservoir bottomhole temperature of 240°F (115°C).
The study field has experienced significant water breakthrough in recent years, which has led to adrastic reduction in the total gas production per well. To increase gas production, it is required toreduce the water-gas ratio (WGR) to prevent the water-source reservoirs from killing the other producing layers and to stabilize the well’s flowing conditions. This could be achieved by shutting off the undesired water production. The main challenge of the study field is the number of reservoirsopened per well (>30 perforated reservoirs), with short distances between the perforated zones. Mechanical isolation was impossible in these cases because it would create restrictions during future interventions.
A multidisciplinary group developed an innovative solution to shut off the water in these wells. The solution included a straddle system that consist of an inflatable retrievable bridge plug used as bottom isolation and an inflatable packer conveyed with coiled tubing (CT) as upper isolation, combined with a chemical water-shutoff treatment. The system was successful in shutting off the watered-outsands while keeping the upper reservoirs producing to date. This CT placement technique opened many opportunities for selective water-shutoff treatments of middle zones. This paper discusses the methodology of the job design, with a detailed operation sequence and results obtained from the field, including production results of some of the treatments pumped in the study field.
