Integrating Digital Tools Optimizes Scale Management

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 218700, “Integrating Digital Tools to Optimize Scale Management: Case Studies,” by Hugh M. Bourne, SPE, Shaun Hosein, and Garry Keilty, BP, et al. The paper has not been peer reviewed. _ The complete paper describes the suite of cloud-based digital-twin tools developed by the operator that provides online, real-time calculation of scale risk and barrier health on a well-by-well basis. The paper presents field case studies in which the suite of tools, integrated into a dashboard, have been implemented. Introduction Several case histories are shared in the complete paper, highlighting the challenges of updating evolving scale risk and monitoring the health of deployed barriers, which drove the decision to create the digital tools to further optimize scale management. Case Study 1 A mature asset with subsea wells had been operated for many years without any history of scaling. The wells were operated under pressure depletion with no water-injection support, but lift gas injection was initiated approximately 10 years ago to maintain production. When a decision was made to increase production from one of the wells by further opening the choke, the potential effect of this change on scale risk was not immediately assessed. Further opening the choke reduced the wellhead pressure by approximately 30 bar, and the well flowed faster, increasing wellhead temperature by as much as approximately 10°C. After an initial increase in production, a decline was observed. A light intervention vessel encountered a hard restriction below the wellhead. When solids were recovered to surface, the tool became stuck in the well and the intervention was stopped while a rig was mobilized to recover the stuck tool. In the intervening period, the recovered solids were analyzed, confirming that the restriction was calcium carbonate scale. Scale predictions were updated with the new operating conditions, confirming that the higher wellhead temperature, coupled with the lower wellhead pressure in the presence of lift gas, had pushed the fluids into a calcite scaling regime. The scale restriction was remediated using acid washing and a preventative scale squeeze treatment. The intervention, in total, cost the operation more than $50 million. Since the scaling event, wells have been routinely squeezed to protect production at a typical cost of around $5 million per well per treatment. Case Study 2 A subsea field is being developed as a tieback to a mature facility. Production from the new tieback has the potential to deposit halite in the wells and flowline at various stages of field life. A multistage wash-water-injection strategy has been proposed to allow a standard tree design. Additional wash water will be injected at the wellhead to protect the flowline from halite deposition as the fluids cool and to ensure that the produced-water chloride concentration is sufficiently reduced. This will create produced water with an almost 1:1 mix of formation water and wash water. Further wash-water injection is planned at the slug catcher. However, the host facility has produced water-handling limitations that restrict the amount of water it can process. Optimizing the amount of additional wash water while managing the halite-deposition risk, ensuring effective corrosion inhibition, and meeting export specification will be essential to minimize deferrals, thereby maximizing production.