In-Situ Stress Test Data - Revelation to Optimization of Stimulation Strategy of an Unconventional Reservoir

摘要

Characterization of in-situ stress is critical for fracture modeling and developing low permeability reservoirs. An optimum stimulation strategy is required to achieve and sustain the economically viable production from such reservoirs with hydraulic fracturing on the basis of robust formation stress information and modeling. The Barmer Basin is situated in Western part India in the state of Rajasthan. Though the main prolific reservoir is Fatehgarh Formation, in northern part of the basin the shallower low permeability Barmer Hill (BH) Formation also contains significant hydrocarbon resources. The reservoir is a finely laminated siliceous unit of probable diatomitic origin with high porosity (25-35%) but low mobility (0.01-0.3 mD/cp). Hydraulic fracturing has been established the key to develop this reservoir. An integrated formation evaluation was undertaken in Mangala Field to address the uncertainty in the in-situ stress properties of different units of the reservoir. Wireline formations tester’s dual packer module was used to measure the in-situ stress in several zones of the Barmer Hill and shallower Dharvi Dunger formations using the micro-frac technique. The shallower Dharvi Dunger (DD) Formation was also a part of the stress testing to achieve the well integrity and confirming as a frac containment unit for Barmer Hill frac growth. In-situ stress data was successfully acquired and profiling in the wells X and Y quantified and proved that a significant stress contrast exists among several layers of the BH and DD Formations. This critical information may lead to the revision of the planned hydraulic fracturing design wherein earlier assumption was less stress heterogeneity in different units. The results obtained were used to calibrate and update the frac model by developing an in-house stress correlation to quantify proper frac growth. This procedure and application can be applied in successful exploitation strategy for other low permeability unconventional reservoirs.