Abstract
Precipitation of the scale in the oil and gas reservoirs, surface and subsurface equipment, and processing and production facilities is a big problem as it affects petroleum production. The scale precipitations decrease the oil and gas production and cause economical loss. Solving this issue requires an engineering investigation to provide a safe, efficient, and economic solution. Consequently, this study proposed a developed dissolver for barium sulfate scales, where two field-scale samples were collected from different locations. The compositional analysis for scale samples showed that sample 1 is 100% barium sulfate where sample 2 has 97.75% barium sulfate and 2.25% of quartz. The composition of the developed dissolver has diethylenetriamine pentaacetic acid (DTPA) as a chelating agent, oxalic acid, and tannic acids as an activator, nonionic surfactant, and water as the base fluid. The new dissolver was investigated with extensive lab tests to determine the dissolution efficiency, precipitation tendency for the dissolved scale solids, corrosion rate, and fluid-rock interaction. The obtained successful results indicated that the developed dissolver had a dissolution efficiency for two real barium scale samples as the results showed 76.9 and 71.2% at 35°C and 91.3 and 78.4% at 90°C for samples 1 and 2, respectively. The new solution has a great performance compared with common scale dissolvers in the oil field as hydrochloric acid, ethylenediaminetetraacetic acid, and diethylenetriamine pentaacetic acid. The developed dissolver showed a very low precipitation tendency for the scale dissolved solids (1.9 and 3.2% for samples 1 and 2, respectively) under 35°C for 24 hours. Without any additives of corrosion inhibitors, the corrosion rate was 0.001835 g/cm2 at 6.9 MPa and 100°C for 6 hours. Injecting the developed dissolver for damaged sandstone core sample with barite mud by flooding test showed a return permeability of 115%.
Highlights
The oil and gas industry suffers from the scale precipitation in the well equipment
The chelating agents were studied for removing the barium sulfate scale; Bageri et al [13] developed a novel solution by employing the diethylenetriamine pentaacetic acid with a special catalyst, and the study results showed an enhancement of the dissolution efficiency for the barium sulfate scale removal
Hydrochloric acid (HCl) acid (15 wt.%), ethylenediaminetetraacetic acid (EDTA) (20 wt.%), and diethylenetriamine pentaacetic acid (DTPA) (20 wt.%) were employed for this comparison, and the results showed that the developed dissolver showed a significant improvement of dissolution efficiency for the two samples
Summary
The oil and gas industry suffers from the scale precipitation in the well equipment. The scale depositions will affect the internal capacity for the well equipment either downhole or at the surface as the production tubing, subsurface valves, wellhead, surface pipelines, and production and processing facilities, in addition to, the reservoir formation [1,2,3,4]. There are many reasons for the scale deposits and exposing many fluid streams during the production cycle was found to be the most critical factor as these streams have different ions and concentrations. These streams might include the oil, formation water, and injected water and will format different types of scales [4]. Many different types of scales are prevalent with the oil and gas field from the sulfate type as barium sulfate which is commonly called barite (BaSO4), calcium sulfate (CaSO4), and strontium sulfate (SrSO4) [8, 9]
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