Analisa Geopressure Pada Sumur Gas Lapangan Sumatera Utara Untuk Evaluasi Problem Partial Loss Pada Trayek 8

Abstract

The drilling of well “ ” experienced a delay in reaching target due to obstacles. Most of non-productive time is caused by problems of well instability such as partial loss. well instability occurs when mudweight used does not match geopressure model of well so that it is not optimal. The use of mudweight in well X is based on geopressure model without a safe mud window approach from nearest well where well is located far enough away that it is less relevant to be used as a reference. Mudweights used are 14.5 - 14.9 ppg on trajectory hole 8 1/2 . Geopressure analysis is carried out using help of Drillwork Predict Software. Geopressure components to be estimated are overburden pressure, pore pressure, fracture pressure, horizontal stresses and collapse pressure. After analyzing geopressure model, safe mud window can be identified, and analysis of drilling problems that occur by examining actual mudweight usage data and formation lithology data can be done. The optimal mud weight to minimize well instability must be greater than collapse pressure but not more than minimum in situ stress. From results of geopressure analysis carried out, it can be concluded that there is overpressure at a depth of 890 m / 1279.5 ft due to disequilibrium compaction. On trajectory hole 8 1 / 2 the mud weight used is too large, causing partial loss. Based on safe mud window obtained from geopressure analysis of well X, optimal mud weight design is 14.67 - 15.4 ppg for drilling on trajectory hole 8 1/2 .