Application of Micro-fine Cement for the Sequential Zonal Abandonment of a Multi-Zone Sand Propped Fractured Horizontal Well With Coiled Tubing - Lab Studies, Field Trial & Computational Fluid Dynamics

Abstract

For the first time in a Danish field, micro-fine cement was used to abandon a multi-zone horizontal well by plugging each sand fractured zone sequentially. Lab testing was performed to investigate the depth of penetration of different conformance systems in a 20/40 sand pack. The micro-fine cement showed the highest penetration and was considered the best option for abandoning sand propped fracs in horizontal wells. The first field application was unsuccessful due to pre-setting of the micro-fine cement in the Coiled Tubing. Extensive lab tests were performed to understand the causes of the pre-mature setting of the cement. A new cement recipe was selected and subjected to modified lab test procedures to successfully abandon the horizontal well. To economically develop chalk reservoirs in the North Sea, long horizontal wells are drilled, hydraulically fractured and waterflooding is applied to the field. To ensure conformance, flow from each fracture is controlled by a Sliding Side Door (SSD). Well A suffered injection water breakthrough which could not be controlled by closing the SSDs. To enable the full abandonment of each zone the decision was made to isolate each zone sequentially from the toe of the well up with cement retainers and to use Coiled Tubing to squeeze a pre-determined volume of special micro fine cement into the zone in order to plug the tubing, the tubing-liner annulus, any cement channels and a limited section of the sand propped fracture. In this manner any potential water channeling between zones and with other wells in the pattern would be prevented. This paper discusses the results of initial lab tests, causes of failure of the first job, testing of new micro-fine cement and the successful application. This paper also discusses the results of computational fluid dynamics simulations which were performed to understand the behavior of cement in a fracture and enable further improvements to similar abandonments in the future.