Filtration Method Characterizes Dispersive Properties of Shales

Abstract

Summary Laboratory and field results show that the Capillary Suction Time (CST) filtration device can be used to characterize the colloidal nature of shale particles, to determine optimal salinity for inhibition, and to analyze drilling-fluid filtrate effect on cuttings dispersion at the wellsite. The concept of potential energy developed between particles is advanced to improve the understanding of borehole stability. Introduction Selection of a drilling fluid to minimize hole problems and to maintain mud stability is a complex problem that requires technical expertise. Generally, drilling operators make mud selections and find solutions to problems on the basis of previous experience in a geologic area. Shale formations are the primary culprits responsible for wellbore and mud stability problems. The time-dependent change and in the filtration and rheological properties of a slurry provides a clue to the nature of a properties of a slurry provides a clue to the nature of a formation problem. The field-adaptable CST filtration device can be used to predict clay behavior and to improve mud selection by measuring the hydrating and dispersion properties of shales. properties of shales. Clays, the active components of shales, have dispersive characteristics that are unique among all other minerals. The silicate matrix of clays develops bond strength between particles from various cations, pressure, temperature, and water present during deposition. Shear and chemical forces present during drilling act on the aggregrated clay bond, causing dispersion of the shales. The dispersive forces acting on the shale can be classified as mechanical and chemical. Mechanical dispersion results from drag forces related to fluid flow and from particles that collide with the rotating pipe, bit, and each other. Chemical dispersion, which causes clay swelling, results from repulsive and attractive forces between the clay and various polar and ionic materials present in the drilling fluid. Aggregation/Dispersion Aggregation/dispersion of drilling muds has been used to describe the size, concentration, and net interaction of particles in a system. Aggregation occurs when particle particles in a system. Aggregation occurs when particle attraction is high and fluid particle interaction is weak, resulting in high gel strengths and filtration rates. Dispersion, or deflocculation, on the other hand, occurs when particle attraction is weak and fluid particle interaction particle attraction is weak and fluid particle interaction is high, resulting in lower gel strengths and filtration rates. Dispersion in fresh water can be compared with deflocculation of clays in salt solutions. Deflocculation is process of breaking down larger aggregates into smaller process of breaking down larger aggregates into smaller aggregates and forming good fluid-particle interaction. Because the CST value reflects the state of aggregation/dispersion of shale slurries, it is necessary to review the fundamental concepts governing aggregation/ dispersion between particles.

Water-based drilling fluids for high-temperature applications and water-sensitive and dispersible shale formations

“…The shale-fluid interaction causes shale instability [20]. Therefore, if a shale formation is drilled with a non-inhibitive water-based mud, the shale instability problems occur [21,22,23].…”

Evaluation of Clay Hydration and Swelling Inhibition Using Quaternary Ammonium Dicationic Surfactant with Phenyl Linker

“…The capillary suction time test was performed to characterize the effectiveness of drilling mud and the inhibition properties of the prepared drilling muds [ 85 ]. The capillary suction time test indicates the amount of free water available in the prepared drilling mud that will invade into the formation of the wellbore.…”

Drilling Fluid Technology: Performances and Environmental Considerations

“…A succinct list of usual methods is presented hereafter: -XRD, X-ray diffraction analysis to determine qualitative mineral content, -CEC, cation exchange capacity to evaluate reactivity of drilled cuttings. The methylene blue test (MBT) method was recommended by API 13I (2003), -GST, a gravimetric swelling test, used to measure water and ion motion during shale/mud interaction (Zhang et al, 2004), -CST, capillary suction time for the determination of filtration properties and salt optimization (Wilcox et al, 1987), -ROP, rate of penetration measured with a penetrometer to estimate the degree and depth of softening or with a Bulk Hardness Test designed to give an assessment of the hardness of shale following exposure to a test fluid (Patel et al, 2002), -DCM, dielectric constant measurement to quantify swelling clay content and to determine specific area (Leung and Steig, 1992), -Triaxial test for pore pressure measurements, carried out in downhole simulation cell (DSC) for compressive stress/strain behavior (Salisbury and Deem, 1990), -Oedometer test for pore pressure modification and chemical potential influence (Bol et al, 1992), -SDT, slake durability test, a standard method originally used in geotechnical studies when measuring the weathering and stability of rock slope: ASTM D 4644-97 (ASTM, 2000), reapproved 1992 (Likos et al, 2004), -Jar slake testing, a qualitative method designed to evaluate shale relative durability in contact with a given fluid. Wood and Deo (1975), Lutton (1977) describe details of this method using six indices, -DSCA, differential strain curve analysis for in situ measuring stress orientation and intensity (Fjaer, 1999), -Hot-rolling dispersion test (shale disintegration resistance or cuttings dispersion test), the most widely used technique in optimizing drilling fluid.…”