In situ stress and reservoir quality evaluation of Jurassic Ahe Formation in Kuqa depression of Tarim Basin, China

The Jurassic Ahe Formation in Kuqa Depression of Tarim Basin shows huge potential for hydrocarbon exploration, however, the stress is intensive due to active tectonic movements. The hydrocarbon exploration process is hindered, therefore, attentions are needed to pay in the stress fields and their controls on reservoir quality. The direction of maximum horizontal stress (SHmax), and magnitudes of SHmax, minimum horizontal stress (Shmin) and vertical stress (Sv) of Ahe Formation were systematically analyzed using image logs, sonic logs and conventional well logs. The controls of in-situ stress fields on reservoir quality (porosity and fracture) are unraveled. The results show that the reservoir pore types include intergranular pores, intragranular dissolution pores and fracture as well as micropores. The SHmax direction is near North-South according to borehole breakouts and drilling-induced fractures, and controls fracture effectiveness. The stress magnitudes control matrix porosity and fracture porosity, and both matrix porosity and fracture porosity decrease with the increasing horizontal stress difference (SHmax-Shmin). Layers with high horizontal stress differences are heavily compacted, and they have no evident pore spaces. Low horizontal stress difference is mainly associated with the fractured zones. The results help predict reservoir quality and fractures of the Jurassic Ahe Formation in Kuqa Depression.