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

Abstract

Hematite was recently introduced as a weighting agent in drilling fluids; however, its use has some problems because of the settlement of solid particles (solid sagging). Particularly when it comes to high-pressure high-temperature (HP/HT) wells, sagging causes inconsistency in the drilling fluid and gives rise to serious drilling operational and technical challenges. This work provides a solution to this challenge via a thorough investigation of hematite sagging in water-based mud for HP/HT applications where ilmenite is combined with hematite. The particles of both hematite and ilmenite were first characterized to address their mineralogical and textural features. Field mud formulation was employed using several ilmenite/hematite contents (i.e., 0/100, 25/75, and 50/50% ilmenite/hematite). Then, laboratory experiments were conducted to study the density, pH, and sag performance of the produced drilling fluids. From the sagging tests, the optimal ilmenite/hematite ratio was determined, and rheology, viscoelastic behavior, and filtration properties of the formulated mud were addressed. The tests were conditioned to 300 psi and 250 °F. The results showed a reduction in mud density and pH with increasing ilmenite content, as the density reduced from15 ppg with base hematite until 14.2 ppg for the 50% ilmenite mixture and the pH reduced from 10.5 to 9.3. The static and dynamic sag tests indicated that the addition of 25% of ilmenite solved the hematite-incorporated sagging issue by well placing the sag tendency within the recommended safe range. The 25/75% combination enhanced the yield point (YP) by 37% with only 1 cP increment in plastic viscosity (PV) and an insignificant effect on the gel strength. The YP/PV ratio was improved by 31% indicating better hole cleaning and solid suspension. The filtration behavior of the 25% ilmenite mixture was superior compared to that of the blank hematite because it resulted in 35, 39, and 35% reduction in the filtrate volume, filter-cake weight, and thickness, respectively. This work contributes to improving and economizing the drilling cost and time by the formulation of a stabilized and distinguished-performance drilling mud using combined weighting agents at HP/HT.

Utilization of Vermiculite for Solving Hematite Sagging in Water-Based Drilling Fluids

“…Comparing the attained results of this work with the previously provided solutions for the hematite sagging issue in the WBDF indicated the technical feasibility of the proposed vermiculite. In the literature, combined ilmenite/hematite 6 Geofluids and Micromax/hematite with ratios of 25/75 and 20/80%, respectively, were proposed for solving hematite settlement showing enhanced filtration characteristics and YP values, but with nonpreferred increment in PV values [20,21]. Also, laponite was introduced as an anti-sag agent with similar behavior [11].…”

“…Different solutions are proposed to mitigate the hematite sagging at both water-and oil-based drilling fluids and experimentally investigated. Some of these solutions used anti-sagging materials such as garamite, laponite, and perlite [11,17,18], while others proposed combining different weighting materials [19][20][21][22]. The research is continued to develop more feasible solutions for the hematite sagging issue.…”

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

“…They can be split into three groups depending on whether they are water-based, oil-based, or gaseous-based. Aqueous drilling muds are the most commonly used because they are relatively inexpensive, have a number of technical advantages, and are less harmful to the environment than other types of drilling muds. − The efficient design and selection of drilling fluid additives are essential to ensure providing the desired mud functions while also preserving the required mud characteristics for successful drilling operations . One of these specified mud additives is the hydrogen sulfide (H 2 S) scavenger that must be included in the drilling mud composition in the sour environment (i.e., H 2 S bearing formations) …”

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

“…The aqueous mud (i.e., water-based mud) is the most commonly used in drilling operations with preferable technical, commercial, and environmental attributes. 5 − 7 …”

“…Thus, the appropriate selection of additives and the proper design of drilling muds are critical factors for successful oil and gas drilling operations. − The drilling mud can be categorized as aqueous, nonaqueous, and gaseous-based mud. The aqueous mud (i.e., water-based mud) is the most commonly used in drilling operations with preferable technical, commercial, and environmental attributes. − …”