Advanced Chemical Water-Shutoff Treatments in Multilayer Gas Reservoirs: A Case Study from Peciko Field, East Kalimantan, Indonesia

Abstract

Abstract The Peciko field is situated offshore of East Kalimantan, Indonesia. The majority of the reservoirs in this field 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 varying 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). Significant water breakthrough was experienced from some reservoirs, which led to dramatically reduced total gas production per well—up to 90% in recent years (water-gas ratio [WGR] ranging from 100 to 1,000 bbl/MMscf). The goal was to reduce WGR to help prevent the water-source reservoirs from killing the other producing layers and to stabilize the flowing conditions. This could be achieved by shutting off the undesired water production. The main challenge of the field is the number of reservoirs opened per well (>25 perforated reservoirs), with short distances between the perforated zones. Mechanical isolation was impossible in these cases because it would create restrictions during future interventions. Previous bullheading methods using water-shutoff chemicals were not always sufficient because theysacrificed producing reservoirs above. Selective treatment with organically crosslinked sealant gel using an inflatable packer as the upper isolation deployed by coiled tubing (CT) and a retrievable bridge plug used for the bottom isolation was successful in shuttingoff the watered-out sands, while keeping the upper reservoirs producing up to date. This paper discusses the methodology of the job design, with a detailed operation sequence and results obtained from the field.