PROBABILISTIC APPROACH TO MODELING AND RISK
ASSESSMENT OF CUTTINGS RE-INJECTION OPERATIONS
Quanxin Guo*
Thomas Geehan
M-I Swaco
5950 North Course Drive
Houston, TX 77072
Voice: 281-561-1476
Fax: 281-561-1420
E-mail: qguo@midf.com
Many cuttings re-injection projects have been carried out worldwide. Operational experience has proved that cuttings injection through hydraulic fracturing is a cost-effective and environmentally friendly means of complying with environmental legislation because of its many advantages. However, the major issue with this technology is to ensure the safe containment of the disposed wastes and to manage the potential risks. Since it is not possible to have all the geological and operational information with total certainty, a probabilistic approach to modeling and risk assessment of cuttings re-injection operations may be more appropriate. For example, prediction of the injected waste extent or disposal capacity depends on whether a single fracture or multiple fractures are generated from the injection operations. When and where secondary fractures are generated may depend on factors such as initial in-situ stress magnitude and orientations, local stress change from cuttings injection operations, and others.
This paper will highlight a probabilistic approach to modeling of disposal capacity and risk assessment in cuttings re-injection operations. Storage mechanisms of multiple fractures are reviewed first and factors contributing to formations of secondary fractures are identified. A Monte Carlo approach is used to evaluate their impacts on disposal capacity and waste extent with associated uncertainties. Implications of the approach and results on cuttings re-injection engineering, operation and monitoring will be given.