Field Trial Results of Novel Percussion Coring in Low UCS Formations

This paper presents the preliminary results of two field trials where a novel percussion sidewall core acquisition tool was deployed. The work continues the development of the new core acquisition technology previously presented by Draper et al. (2022) and Lakshtanov et al. (2022). This technology leverages digital rock physics (DRP) to assess core quality. A novel percussion sidewall core acquisition method was trialed in two appraisal wells targeting carbon capture and storage (CCS) prospects. The percussion bullets used included an internal sleeve that protects the core samples from handling damage during extraction and analysis. The percussion sidewall sampling was part of an extensive evaluation program that also included whole core and rotary sidewall core acquisition. Coring program targets were sandstone intervals predicted to have low unconfined compressive strength (UCS), and core recovery was expected to be a challenge. The novel percussion method was deployed to test the acquisition technology under real field conditions and provide a basis for validating the merits of the method against conventional coring and core analysis methods. Percussion core samples were acquired during individual wireline runs in two field trial wells. On the first well, tool problems unrelated to the novel bullet design resulted in core recovery, which was lower than expected. Modifications were applied, and very high core recovery was achieved on the second well. High-resolution X-ray micro-computed tomography (micro-CT) images of the core samples indicated that a suitable volume of material was available for DRP and conventional percussion core sample analysis. Preliminary assessments indicate that the method is competitive with other rock sampling methods in terms of cost, risk, and value. Deployment of a novel percussion sidewall coring technology in two field trial wells has demonstrated the applicability of the sleeved bullet concept to real downhole conditions. DRP and conventional evaluation of the core samples have shown that samples are of good quality and can yield critical reservoir characterization information. The novel percussion coring technology addresses several historic challenges to characterizing soft (low UCS) formations. Combined with DRP and conventional core analysis, this technology offers a cost-effective and efficient method of reservoir characterization.