The effect of salts and haematite on carboxymethyl cellulose–bentonite and partially hydrolyzed polyacrylamide–bentonite muds for an effective drilling in shale formations

Abstract

A common issue encountered by drilling engineers during drilling operation in oil and gas industries is that simple waterbased muds are not suitable for deeper depth and certain clay-swelling formations. Another option as to increasing the density of the drilling mud which brings about an increase in filtration loss, additives may be added to improve the fluid properties. This paper aims on determining the effectiveness of common salts, sodium chloride (NaCl) and potassium chloride (KCl), and haematite on the rheological properties of optimized carboxymethyl cellulose (CMC)-bentonite and partially hydrolyzed polyacrylamide (PHPA)-bentonite muds. Both CMC and PHPA polymer act as fluid loss-reducing agents and viscosifiers for normal bentonite water-based mud. The mud is further enhanced to counter certain swelling formations such as shale through the addition of NaCl and KCl. These salts inhibit the shale formation from swelling through its ions by entering the lattice of the drilling mud or formation instead of the water ions. Haematite, on the other hand, basically functions to increase mud density and acts as a substitute for barite. The effect of haematite on drilling fluid was studied because it gives higher degree of rheological parameters and increases density as compared to barite. So, an optimized concentration of additives was determined for both CMC-bentonite and PHPA-bentonite mud systems, respectively. Three grams of KCl and 3 g haematite were used for CMC-bentonite mud, while 3 g KCl and 1 g haematite were added into PHPA-bentonite mud. Both these muds have shown swelling reduction as compared to those without the use of additives. Moreover, they exhibited Herschel-Bulkley fluid behaviour according to the power law model where their 'n' value was less than 1, while their yield points were more than zero. Since shale sloughing is a major problem faced during drilling operation, it leads to major complications in drilling. So, finally, both the formulated drilling fluids are tested to analyse their effect in shale formations by static immersion test. The shale rock was collected from Champhai District of Mizoram. Both the formulated muds exhibited great results as swelling in shale rock was reduced for both muds and optimum rheological values were maintained.

Effect of pH on Rheological and Filtration Properties of Water-Based Drilling Fluid Based on Bentonite

“…Akinade et al [35] showed that the bentonite clay needed further improvements to be used in the drilling fluids to provide an optimum mud rheological and filtration properties as API standards. Kuma et al [36] provided a study for the bentonite-based mud for properties improvement. The study tested adding carboxymethyl cellulose, sodium salt, partially hydrolyzed polyacrylamide (PHPA) polymer, and polyacrylamide, and the results showed an improvement in the mud rheological and filtration properties.…”

Application of High-Density Brines in Drilling and Completion Fluids: Current Insights and Future Perspectives

“…NaCl also demonstrates higher attraction toward the water molecules that make it easy to dissolve in water in massive quantities. NaCl improves the shale inhibition features of drilling muds . It prominently improves the lubrication features and enhances the capacity of the drilling muds to suspend solid particles .…”

Comparative Analysis of Carboxymethyl Cellulose and Partially Hydrolyzed Polyacrylamide – Low-Solid Nondispersed Drilling Mud With Respect to Proper-Ty Enhancement and Shale Inhibition

“…The values for the three types of mud were then plotted and compared. The formula for swelling is given below [10]:…”

“…CMC coats cuttings and protects them from hydration. In addition, CMC enhances drilling fluid properties [10]. CMC is resistant to bacterial attack and can maintain flow properties under high-temperature, i.e., up to 135 °C (275 °F), and high-pressure conditions in the presence of bentonite clay [9].…”