Dispersing Settled Barite: An Approach to Improve Performance and Safety of Cut and Pull in Plug and Abandonment Operations

Abstract

Summary Settled barite is a known challenge in well construction and well control activities. This phenomenon creates operational and safety challenges during cut and put operations in well abandonment activities. In this paper, we introduce a novel approach to mitigate these challenges by dispersing settled barite particles using chelating agents, specifically ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA), commonly utilized in the oil industry to dissolve barite scales. Laboratory tests were conducted to assess the impact of these two chelating agents across varying concentrations, weight-to-volume ratios, pH levels, and durations. Settled barite samples retrieved from a plug and abandonment (P&A) operation were used in this test. Initially, visual inspection suggested some action of chelating agents in fragmenting settled barite materials into smaller particles. Afterward, a sequence of sieves was used to assess the particle-size distribution (PSD) and quantify the dispersion, revealing an increase in particle dispersion correlating with higher concentrations of chelating agents and weight-to-volume ratios. Contrary to scale-dissolving experiments, the dispersion of settled barite manifests across a broad pH spectrum. Furthermore, an initial increase in dispersion was observed over time, while the introduction of an activator such as potassium chloride (KCl) displayed no discernible effect on the overall dispersion process. This work shows the potential resolution of settled barite issues through the application of conventional chelating agents, such as EDTA and DTPA, commonly used within the oil field. It suggests methodologies for optimizing their performance in addressing barite settlement concerns. In addition, the study proposes the broader applicability of chelators within the EDTA and DTPA family for dispersing settled barite, thereby enhancing performance and augmenting oilfield safety in chelator use.