Barite–Micromax mixture, an enhanced weighting agent for the elimination of barite sag in invert emulsion drilling fluids

Abstract

Weighting agents are mixed with the drilling mud to provide the high density required to control high-pressure high-temperature (HPHT) wells throughout the drilling operation. Solids sag occurs when the weighting agent separates from the liquid phase and settles down, causing variations in the drilling fluid density. This study evaluates barite-manganese tetroxide (Micromax) mixture to eliminate solids sag issue encountered with weighted invert emulsion drilling fluids at HPHT conditions. Micromax additive was added to barite-weighted fluids in different concentrations, 0, 15, and 30 wt% of the total weighting agent. Static and dynamic sag tests were used to evaluate the sag tendency of the new formulation under static and dynamic conditions. The performance of the new formulation was evaluated by measuring the electrical stability, density, rheological, viscoelastic, and filtration properties of the drilling fluid. The obtained results showed that Micromax additive improves drilling fluid stability by reducing the sag tendency. Adding only 30 wt% of Micromax additive eliminated barite sag issue in both dynamic and static conditions at 350 °F. 30 wt% Micromax increased the base fluid density by 5.4% and the yield point by 115% and maintained the gel strength value at 12 lb/100 ft 2 , while it reduced the plastic viscosity by 30%. The addition of Micromax additive improved the viscoelastic properties of the drilling fluid by maintaining a higher storage modulus to the loss modulus ratio when compared with the barite sample (in the range 4-4.5). Furthermore, 30 wt% Micromax improved the filtration performance by reducing the filtrate volume, filter cake weight, and filter cake thickness by 50%.

Barium Sulfate Scale Removal at Low-Temperature

“…One of the hardest scale types is the sulfate scales that are commonly formatted due to the incompatibility between the two water streams of production and injection water, and this scale type is a hard scale for removal as it has a low dissolution rate with acid [11]. The barium sulfate (barite) is commonly used with the drilling fluids to obtain the required mud type for well control issues [12,13], and the incompetent practices and poor design during the drilling operations might cause formation damage by the barite solids precipitations in the drilled rock pore system [14][15][16]. Many sulfate scales are precipitated in the reservoir section and the well pumps of artificial lift equipment [17].…”

Impact of Perlite on the Properties and Stability of Water-Based Mud in Elevated-Temperature Applications

“… 3 This increase of yield point and gel strength indicates the enhancement in the mud capability to keep the solid particles in suspension and reduce the sag tendency at dynamic and static conditions, confirming the sag test results. 26 , 34 , 35 Another advantage of using perlite with high-density mud is enhancing yield point to plastic viscosity ratio (YP/PV). Perlite additive increased the YP/PV significantly from 1.31 to 2.58 to fall within the recommended range as per drilling practices (1.5–3).…”

“… 20 − 23 Many parameters contribute to the sagging phenomenon, such as drilling fluid properties, weighting agents, particle size, downhole conditions, time, pipe rotation, well inclination, and well geometry. 24 − 26 The sagging phenomenon mechanism is that the solid particles separate from the liquid phase and start to accumulate downhole, causing the density of the drilling fluid column to vary with the depth ( Figure 1 ). Consequently, the mud weight becomes less than the formation pressure in the upper parts of the drilled section, which may cause a severe well control issue.…”

The Role of Drilled Formation in Filter Cake Properties Utilizing Different Weighting Materials

“…12−17 Furthermore, other researchers used a mixture of several weighting materials with the aim of mitigating drilling instability issues such as barite sagging and of improving the drilling mud properties. 8,18 Also, nanoparticles were investigated as weighting agents by several studies that showed a general improvement in the drilling fluid properties. 2,19−22 Accordingly, selecting the right weighting material is not a trivial task and it depends on many factors including the cost, the required properties (i.e., density), and its solubility in conventional filter cake removal treatments since it affects approximately 70−80% of the filter cake structure.…”

“…Many materials were used as weighting agents over the years, and researchers are still looking for new materials and ways to improve the existing ones. Examples of common weighting materials include barite, calcium carbonate, ilmenite, hematite, manganese tetroxide (Micromax), galena, stibnite, and potash. − One potential method to improve the weighting material performance is by reducing its particle size; this introduced more options such as micronized barite, micronized ilmenite, and micronized manganese tetroxide as weighting materials. − Furthermore, other researchers used a mixture of several weighting materials with the aim of mitigating drilling instability issues such as barite sagging and of improving the drilling mud properties. , Also, nanoparticles were investigated as weighting agents by several studies that showed a general improvement in the drilling fluid properties. ,− Accordingly, selecting the right weighting material is not a trivial task and it depends on many factors including the cost, the required properties (i.e., density), and its solubility in conventional filter cake removal treatments since it affects approximately 70–80% of the filter cake structure …”