Process and Lessons Learned Using Hollow Glass Spheres for Drilling Depleted Fields

Abstract

Two major mature oilfields with multiple rigs (> 150) delivering hundreds of thousands of drilled metres annually, suffered from severe induced losses during their ongoing development and also redevelopment phases. These events of course significantly impacted the overall drilling performance, leading to substantial production issues and poor economics. Although the fundamental underlying nature of the losses varied; proven success in both cases was to significantly reduce the mud weight. Additionally, in both cases, the key to achieving this needed to be a solution using low-cost, minimal rig modification approaches while at the same time retaining the well productivity at equivalent levels. The applied solutions Team both identified and screened a number of approaches for achieving an effective MW reduction, and this process resulted in the proposal for the use of Hollow Glass Spheres (HGS) as the preferred methodology. A thorough study of the available literature and previous industry experience had demonstrated that HGS potentially met all of the requirements. In order to confirm the compatibility of the HGS, a series of laboratory tests were planned and performed; followed by a set of structured field trials, confirming the suitability of this technology. These results were then collated into a Basis of Design (BoD) for a drilling fluid system utilising HGS for drilling through target zones with abnormally low pore pressures, capturing lessons learned from all stages of their application. This paper will describe the details of the screening for the available solutions; as well as performing the feasibility study through laboratory tests and field trials. It will report on the phased approach taken for piloting the technology, describing the challenges and risks that were assessed, faced, and mitigated during both the testing and trialling stages. A review of the post-deployment lessons learned, techniques used, and approaches corrected during subsequent trial period(s) will be presented. A summary of the economic assumptions made, and their evolution will be covered; and then discussed with regards to technology upscaling and the further proposed developments and enhancements. The results of the HGS technical solution have greatly exceeded the original expectations and continuous improvement of the technology indicates much more to come. Discussions of the possible modifications and improvement to the HGS fluid system are ongoing and involve formulation, HGS type, logistics, strategy of HGS mud utilisation … etc. The use of HGS on these two oilfields has been novel and has resulted in a generally greater interest and appetite within the industry for this area of application.