ABSTRACT:

Performance and environmental assurance of cuttings injection programs require monitoring and periodic analysis of injection response. Such programs provide operational oversight and the ability to respond to changes in performance, providing for optimization of operating parameters to minimize potential negative impacts. Cuttings injection was implemented on a remote pad in the Cashiriari Field, located in a nature preserve in Camisea, Peru. CI was recognized as a technically and environmentally acceptable alternative for waste management in a location with extreme environmental sensitivity. Higher than anticipated injection pressures, indicative of regional and local stress regimes, required adjustments in operating parameters and expectations. Performance was contingent on successful inhibition of reactive clays in and around the target zones. Continuous monitoring of closure pressure and other trends associated with batch injection has made performance predictions possible. Monitoring operations have allowed for performance improvement and/or minimization of potential problems. The operation injected over 212,000 bbls of cuttings on the first pad and continues to be successful on the second pad through careful management of batch attributes and adaptation to operating realities. Assurance derived from such programs provides long term operational viability and social acceptance of cuttings injection as a safe means of waste management.

1. INTRODUCTION

Assurance of a successful and environmentally sound long-term cuttings injection program requires monitoring and periodic analysis of injection performance response.1,2 Such a program provides for operational oversight and the ability to identify changes in performance response or trends, thereby providing for modification of operating parameters to optimize performance and minimize the negative impact of unexpected responses.3,4,5 An implementation of this process was instituted for a remote, pad-drilled site located in a nature preserve in the Amazonian rainforest of Peru. The development of natural gas reserves at Camisea has extreme environmental sensitivity and injection of the generated drill cuttings was recognized as a technically and environmentally acceptable alternative for drilling location waste management. A number of issues were encountered in implementing and operating the DCI project at Cashiriari. Higher than anticipated initial injection pressures were indicative of the stress regime of the region and required an adjustment in thinking with respect to operating parameters and performance expectations. A number of issues were encountered in implementing and operating the DCI project at Cashiriari. Performance has been contingent on successful inhibition of the reactive clays adjacent to the relatively thin sandy target zones. Continuous monitoring has allowed projections of the closure pressure increases associated with batch injection through time, providing a prediction of future performance and disposal capacity. Information gathered from monitoring operations has allowed for performance improvement and/or minimization of potential problems identified. The operations at Cashiriari 1 successfully injected over 218,000 bbls of cuttings through careful management of batch attributes and adaptation to operating realities.

2. PRELIMINARY STUDIES

Geomechanical models of the potential disposal lithologies were developed as part of engineering feasibility studies. Formation mechanical properties were evaluated and stress profiles developed that identified potential disposal zones during engineering design studies for each of the sites.

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