Prevention of Hematite Settling in Water-Based Mud at High Pressure and High Temperature

Experimental Investigation of Using Manganese Monoxide as a Hydrogen Sulfide Scavenger for Aqueous Drilling Fluids

One of the most serious safety and health concerns during drilling oil and gas wells is the potential release of hydrogen sulfide (H2S) to the surface, exposing workers to high risks. Serious corrosion-related damage to handling equipment is also inevitable in the presence of H2S. Various H2S scavengers have been utilized, but each has its pros and cons; hence, research is continuing to develop an optimum and feasible scavenger. Since manganese monoxide (MnO) is a reactive metal oxide with high oxidation and absorption capabilities, it may have the potential to effectively scavenge H2S during drilling operations when included in drilling mud formulations. Consequently, the key aim of this work is to investigate the H2S scavenging performance of the aqueous drilling fluid containing MnO. This work studied the impact of MnO addition on the drilling mud's alkalinity, rheological behavior, filtration performance, and corrosion tendency. The experiments were also conducted for mud without a scavenger and a fluid containing the SourScav commercial scavenger, which serves as a benchmarking reference. The findings demonstrated that MnO performed exceptionally well for H2S scavenging where it boosted the aqueous mud's scavenging capacity from 84.3 to 426.2 mg of H2S/L of mud, showing more than 400% improvement relative to the base mud. Additionally, this scavenging performance is about 2.1 times higher than that of the commercial scavenger. As opposed to SourScav, MnO maintained the mud's pH at a safe level above 10. The addition of either MnO or SourScav did not weaken the mud rheology and provided practically satisfactory rheological parameters. Both SourScav and MnO marginally increased the formed filter-cake thickness from 2.9 to 3.9 mm with a slight increment in the filtrated volume but still within the acceptable limits. The corrosion test indicated the noncorrosive characteristics (i.e., the corrosion rate was nearly zero) of MnO and the commercial scavenger. This study illustrates the promising utilization of MnO as a cost-effective H2S scavenger, enhancing the efficiency and safety of drilling operations.

Evaluation of Using Fly Ash as a Weighing Material for Oil-Based Drilling Fluid

Innovation and sustainability are essential in the fast-changing oil and gas business. Fly ash, a byproduct of coal combustion in power plants and factories, has become a valuable resource in many industries, changing the concept of waste materials. Fly ash is essential to sustainable development and environmental care due to its unique qualities and multiple applications. In the drilling industry, a well-designed drilling fluid is essential and this requires the use of various additives that serve specific functions to achieve a successful borehole. This study investigates the use of fly ash as a weighing material in oil-based mud, with the intent to develop an economically acceptable drilling fluid system using industrial waste. The study compared fly ash to three commonly used weighing materials in the drilling industry: calcium carbonate (CaCO3), barite (BaSO4), and ilmenite (FeTiO3). Drilling fluids were prepared using these weighing materials at various weights, and their properties (density, electrical stability, rheological features, and filtration properties) were measured using API-recommended methods. The rheology and filtration tests were conducted at elevated temperatures (350 °F). The results indicate that fly ash has the potential to be a useful weighing material in drilling operations. It can increase the fluid density up to 10 ppg without affecting the rheological properties at 350 °F. Additionally, the electrical stability of the drilling fluid was enhanced compared to the other used weighing materials. The addition of fly ash also improved rheological characteristics such as plastic viscosity, yield point, and gel strength without affecting HPHT filtration properties. The carrying capacity was improved by 53 and 86% over calcium carbonate and barite, respectively. Overall, the findings suggest that fly ash can be a viable alternative to other weighing materials in the recommended density range.

Improvement of Hydrogen Sulfide Scavenging via the Addition of Monoethanolamine to Water-Based Drilling Fluids

The release of the lethal hydrogen sulfide (H₂S) gas during the drilling of sour subterranean formations is of huge health and safety concern. Additionally, the contact of this corrosive gas with handling equipment might result in severe damages and significant economic losses. Accordingly, effective in situ scavenging of H₂S while drilling is very crucial. Thus, we report herein the addition of monoethanolamine (MEA) to water-based mud with the objective of improving the H₂S-scavenging efficacy of the mud. The H₂S-scavenging capacity was evaluated for the MEA-containing mud and compared with the base mud and fluids containing the commercial scavengers, SourScav and triazine. Also, the key mud characteristics including rheology, filtration properties, alkalinity, and corrosion rate were investigated in the presence and the absence of MEA, and the obtained results were compared to those of SourScav and triazine. The obtained experimental results revealed that the addition of MEA to the base mud significantly improved the H₂S adsorption capacity of the base mud by 117%, compared to 50 and 74% with the SourScav and triazine. Additionally, the pH value of the MEA-containing mud complied with the practical recommendations for drilling in a sour environment. Moreover, the plastic viscosity was increased by 13% to 37 cP with the MEA-containing mud with an insignificant impact on the yield point. Furthermore, the MEA-containing mud showed a favorable zero corrosion rate, as was the case for SourScav and triazine muds. However, unlike SourScav and triazine, MEA did not substantially enhance the filtration performance. Nonetheless, the filtration characteristics of the MEA-containing mud were still better than the base mud and within the recommended practical range for water-based muds. Overall, the results presented in this study reveal that the addition of monoethanolamine to water-based muds improves the mud characteristics and, more importantly, provides a superior H₂S-scavenging performance relative to SourScav and triazine scavengers, suggesting the commercial relevance of MEA for drilling applications.