Successful Conversion of a Drill Cuttings Reinjection (CRI) Well into a Produced Water Disposal (PWD) Well: A Unique Case Study from the Middle East

To address the high demand for produced water management, a Cuttings Reinjection (CRI) well (well-1) was converted into a Produced Water Disposal (PWD) well. The study outlines the methodology, results, challenges, and cost savings associated with this conversion. The target reservoir for existing PWD wells consists of multiple layers of limestone and dolomite. An extensive study was conducted to plan the PWD wells in this target zone, supported by production logging tools (PLT) & core data. Initial injectivity results indicated that well-1's performance (bare footed completion) was fair, and it was comparable to nearby well's performance, having same completion design. The injectivity test was also compared with an existing CRI well (well-2) in the same area, having different completion design. After the initial injectivity test, well-1 remained active as a CRI for five years with low injection rates, followed by another five years of being shut-in due to surface facility constraints. Given the high demand for produced water management, it was considered whether to evaluate a new PWD well locations or opt to a cost-effective option to reactivate well-1 as PWD, given the surface slots are limited. Because of this, an integrated approach was used for evaluation, focusing on geological (such as Temp logs, etc.) and geophysical data (such as seismic, etc.). Injectivity tests were performed in well-1 at different depths, guided by attribute maps. Due to poor performance results, the injectivity test was repeated after each acid stimulation job till the desired results were achieved. Following a detailed geological and geophysical evaluation, two prolific zones were identified as potential candidates for sustainable injection. Seismic reservoir characterization revealed the distribution of cavities (karst collapse features) within the target zones, which correlated well with dynamic mud losses. Based on the performance of nearby wells and results from seismically driven attributes, optimum locations were considered for new PWD wells. The attribute map also showed that well-1 targets a highly porous zone, as confirmed by the initial injectivity results. However, the first injectivity test conducted after ten years yielded extremely poor results. The injectivity test after third acid stimulation job showed slight uplift in improvement, though still lower than the initial injectivity performance. Subsequently injectivity tests were repeated after every acid stimulation job. The last injectivity test after the seventh acid job showed a two-fold improvement in water injection compared to the initial results. Based on the strong injectivity result after the seventh acid stimulation job, it was decided to activate well-1 as a PWD. Well-1 has now been active as a PWD for over a year, showing sustainable performance. This conversion resulted in saving a surface slot along with over $10MM incremental savings in CAPEX/OPEX. Converting a CRI into a PWD well is not common due to completion design constraints, injection performance, and target Formation heterogeneity. Consequently, this unique study focused on post-conversion results to validate that the well can be switched from a CRI to a PWD or vice-versa without any changes in completion design and extra cost implications.