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Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Formation Evaluation Challenges in HPHT Tight Sand Reservoirs
(1) Schlumberger, Mumbai, India.
(2) Gujarat State Petroleum Company, Gandhinagar, India.
Rising demand for energy has pushed the oil & gas exploration and production operations to harsher environments. High pressure and high temperature (HPHT) is one of such challenging areas. Conventionally, wireline log measurements are rated for operations up to 350 degF temperature and 20,000 psi pressure. However, since many reservoirs exceed these pressure and temperature limits, HPHT wireline tools have been developed. The most significant challenges occur at “Ultra-HPHT” environment, i.e., at 400-500 deg F and up to 35,000 psi, which represents the practical upper operating limit of the existing logging tool electronics technology.
Indian HPHT operations have seen remarkable growth in the past few years. More specifically, the gas field operations in Krishna Godavari (KG) basin, offshore of Andhra Pradesh, east coast of India, qualify as Ultra HPHT environment. During the KG exploration activities numerous operational challenges were encountered due to extreme HPHT conditions.
This paper presents experience gained in drilling and formation evaluation of deep tight gas reservoirs at ultra HPHT conditions in the KG basin. Moreover, new technologies and formation evaluation methodologies used to address HPHT related challenges are discussed along with recommendations for future HPHT operations.
More specifically, the paper highlights the data acquisition challenges in the ultra HPHT environment and presents an innovative formation evaluation technique using wireline logs at HPHT conditions to optimize the perforation strategy in tight gas reservoirs in the absence of resistivity logs. Moreover, borehole stability related problems were evaluated and a Mechanical Earth Model was developed to improve the drilling performance at HPHT conditions. The paper describes the application of the model in the exploration wildcat environment. The material presented will facilitate other well construction teams facing challenging drilling objectives in similar hostile remote environments.