Applications of Geomechanics in the Development of the Naturally Fractured　Carbonates of the Mara Oeste Field Venezuela

摘要

A geomechanical study for naturally fractured carbonates wasrnperformed as part of an integrated study for the Mara Oesternfield in Venezuela. The study included working with onernpaleomagnetically-oriented core in which natural and inducedrnfractures were identified and oriented. Geomechanical staticrnand dynamic laboratory tests were performed, to obtainrnstrength, deformability and failure characteristics of the rocks.rnThe in situ stress field orientation was determined in one wellrnby using special core techniques such as ASR, DSA, AAA andrnSWAA. Regional information provided by focal mechanismrndata available in the Maracaibo basin was integrated togetherrnwith image logs for eleven wells. Natural fractures andrnbreakouts were studied and fracture orientation and in siturnstresses were related with geological structures present in thernfield. A stress orientation map was built with all the availablerndirectional information. In situ stress magnitude was estimatedrnby lost-circulation data, extended leakoff test and backanalysisrnfrom breakouts. A three-dimensional stress model ofrnthe field was performed using a lagrangian finite differencerncode. The model showed that stress orientation is dependentrnon geometry of the layers, and faulting can introduce jumps inrnstress magnitude. Out from the influence of the main faults thernmodel reproduced the regional trend of stresses. Close to thernmain fault of Mara Oeste, stress rotation was evident both inrndepth and spatially, particularly at the crest of the folds. Thernmodel provided estimates of in situ stress magnitude that canrnbe used to design new wells in blocks with little information.