A unique data acquisition plan was customized to fit the requirements of the assessment needed for reservoir-scale storage capacity and caprock integrity. The occurrence and orientation of the natural fractures are controlled by regional plate tectonics and rock mechanical properties; these fractures have an outsize influence on reservoir quality and productivity. An optimized data acquisition and evaluation strategy was necessary. An additional fracture set with a different orientation had the potential to change the whole strategy of well placement, seal integrity, and reservoir characterization understanding.
The analysis of image logs and sonic data from both wells demonstrated the complexity of fracture networks in this field, emphasizing the need for data integration to better characterize the fractures present.
In two wells, a high-resolution borehole image combined with 3D far-field sonic service data were acquired via conveyance on the ThruBit™ through-the-bit logging services. Detailed fracture characterization was accomplished by integrating the borehole image with sonic reflection information within the reservoir. In one deviated well (Well-A) in the study area, a high-resolution borehole image combined with multidimensional far-field sonic data were acquired. The sonic reflection imaging identified three distinct fracture sets: Two of them were parallel to the well trajectory and were invisible to the borehole imagery. Therefore, a subsequent well was drilled (Well-B) orthogonal to Well-A, and both measurements showed consistent results, confirming the new fracture sets identified in Well-A and validating the results.
The findings proved that the area was subject to more than one cycle of fracture-developing tectonic movements, which can aid in carbon-injection strategy and reduce the uncertainty associated with gas flow modeling and the seal integrity analysis.
