Advances in Wireline Conveyed In-situ Reservoir Stress Testing Measurements: Case Studies from the Sultanate of Oman

One of the major fields in the South of the Sultanate of Oman produces oil at 94% average BSW. All produced water is disposed of without treatment into the same aquifer. The disposed water is injected under fracing conditions and takes place more than 200 m below the lower shale (cap rock) in the sandstone (Fig.1). However the failure of the field's cap rock could result in oil deferment and the contamination of the overlying aquifer; therefore rigorous risk management is strongly required.Several in-situ stress testing (mini-frac) stations were conducted in the field focusing on lower shale and sandstone formations to evaluate the risk of breaking the cap rock and above formations associated with the water disposal. However this was very challenging using the normal ways of testing; hence the stress testing application was conducted with an oil based viscous fluid. The viscous fluid allowed accomplishing the objectives in higher permeability and shale zones. The oil based viscous fluid facilitates initiation of a fracture in highly permeable sandstone formations and reduces the osmosis and plastic behavior effects in shale zones.The viscous fluid stress testing provides the results required to update the numerical models for each formation by obtaining minimum stress and fracture initiation, propagation, and closure pressures (frac gradients). Moreover the test results will help to build models that can predict fracture growth while injecting water. This paper will discuss in detail the viscous fluid stress test and how the results can be used to understand the reservoir behavior. Realistic injection forecasts were made possible using commercial fracture simulation software and some analytical and diagnostic methods based on pressure survey and injection volumes history.

show abstract

Integrated Acoustic, Mineralogy, and Geomechanics Characterization of the Huron Shale, Southern West Virginia, USA

Franquet

Mitra

Warrington³

et al. 2011

All Days

View full text Add to dashboard Cite

Exploitation of unconventional shale gas reservoirs depends on successful hydraulic fracturing and horizontal drilling. Mineralogy, organic matter content, acoustic anisotropy, and in-situ stress all play an important role for well completion design. As part of a comprehensive site study of the Upper Devonian Huron shale, borehole acoustic and mineralogy logging data, in addition to conventional logs, were acquired in a vertical well prior to hydraulic fracturing and microseismic monitoring of a series of laterals drilled from the same location. The acoustic data was processed for compressional wave, cross-dipole shear, Stoneley-derived horizontal shear, radial velocity variations, and borehole Stoneley reflectivity indicators. The cross-dipole anisotropy and the near-well radial slowness variations provided information about intrinsic anisotropy and stress sensitivity to determine the source of dipole-mode anisotropy. Significant transverse acoustic anisotropy was detected and used to obtain vertical and horizontal dynamic elastic properties. The mineralogy and petrophysical analysis were used to generate a micromechanical constitutive model to reproduce numerically the laboratory stress-strain behavior of the rock, from which quasi-static mechanical properties were determined. These were calibrated against triaxial tests on core samples from an offset well, and the vertical and horizontal static elastic rock properties were used to estimate the vertical variation of the horizontal stress. The resulting stress profile, along with accurate mineralogy and petrophysical analysis, provides important information to select the best vertical locations of lateral wells and to identify natural fracture barriers.

show abstract

Advances in Wireline Conveyed In-situ Reservoir Stress Testing Measurements: Case Studies from the Sultanate of Oman

Cited by 6 publications

References 1 publication

Integration of mini-frac stress results with core data to identify ductile behavior of overpressured sandstone reservoir in deep-water offshore Krishna-Godavari basin, India

Integration of mini-frac stress results with core data to identify ductile behavior of overpressured sandstone reservoir in deep-water offshore Krishna-Godavari basin, India

Innovative In-situ Reservoir Stress Test Helped to Manage and Optimize Water Disposal under Fracturing Conditions in South Oman

Integrated Acoustic, Mineralogy, and Geomechanics Characterization of the Huron Shale, Southern West Virginia, USA

Contact Info

Product

Resources

About