Effect of the Filtrate Fluid of Water-Based Mud on Sandstone Rock Strength and Elastic Moduli

Abstract

During drilling operations, the filtrate fluid of the drilling mud invades the drilled rock. The invading filtrate fluid will interact with the rock and therefore alter the rock internal topography, pore system, elastic moduli, and rock strength. The objective of this study is to evaluate the effect of the mud filtrate of barite-weighted water-based mud on the geomechanical properties of four types of sandstone rocks (Berea Buff, Berea Spider, Bandera Brown, and Parker). The mud filtrate was collected to provide mud filtrate–rock exposure at a pressure of 300 psi and 200 °F temperature for 10 days. The study assessed the alteration in the rock geomechanics employing an integrated laboratory analysis of X-ray diffraction (XRD), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and scratch testing. The ultrasonic results showed changes after exposure to the mud filtrate and an obvious reduction trend in the shear wave velocities due to the dissolution and mineralogical modifications in rock samples. The obtained results displayed a general strength reduction for the four sandstone types with different levels. The strength reduction ranged from 6% reduction for Berea Spider to a record 23% reduction for Parker. For all sandstone types, Young’s modulus showed a general reduction ranging from 11 to 40%, while Poisson’s ratio recorded an increase by 62–155% after the filtrate interaction. The study illustrated the role of pore-system alteration in controlling the rock strength and dynamic moduli.

The impact of overbalance pressure on the alteration of sandstone geomechanical properties

“…The sandstone-mud exposure was studied under different downhole conditions of exposure time, clay type and content, different mud weighting materials, and mud filtrate impact (Gamal et al 2021a, c), while the current study presents the role of overbalance pressure on this interaction. The extended exposure time from 30 min to 5 days was found to have significant deterioration to the rock strength as the results showed 18% strength reduction was recorded after five days of mud-rock exposure under 300 psi overbalance pressure and 200°F temperature, in addition, the rock elastic properties showed alterations and the study covered the internal changes to the pore system due to the mud solids precipitations and clay swelling (Gamal et al 2020a(Gamal et al , 2020b. The mud filtrate impact on four sandstone rock samples that show different clay types and content, and the results illustrated that the rock strength decreased with a different trend for each sandstone formation (Berea Buff and Spider, Bandera Brown, and Parker) that shows different behavior due to the clay content, clay type, and quartzclay frame (Gamal et al 2021b(Gamal et al , 2020aHe et al 2019).…”

“…Due to the drilled formation exposure to the drilling mud, the chemical activity of the mud and the mineralogical composition of the formation will play a critical role in the mud-rock chemical and mechanical interactions, and hence, many changes will arise to the internal pore structure of the drilled formations in terms of pore plugging due to solids precipitations and/or dissolution and pore opening (Cao et al 2019;Gamal et al 2020a;Meng et al 2005). Consequent alterations will be observed in the rock characteristics in terms of porosity, permeability, fluid flow properties, internal rock topography, pore system, elastic properties, and rock strength (Gamal et al 2020c;Chukwuemeka et al 2017;Sharma and Wunderlich, 1987).…”

“…Hence, technical aspects have to be considered as well control, depleted zone pressures, and formation integrity (Erivwo and Makis, 2021). By the action of this pressure, the mud solids with the filtrate will invade the pores of the drilled rock and will go for further interaction process with the internal pore system of the rock, and severe changes might occur for the rock structure (Gamal et al 2020a;Sharma and Wunderlich, 1987;Windarto et al 2011).…”

Effect of Different Weighting Agents on Drilling Fluids and Filter Cake Properties in Sandstone Formations

“…Over the years, a variety of drilling fluid additives have been recommended to form a desired filter cake layer to withstand the HTHP drilling . Withstanding the due importance of the filter cake layer, various tools are introduced to characterize the filter cake including X-ray computed tomography (CT scan), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM). ,,, The properties of the filter cake layer including the thickness, porosity, and permeability are very sensitive to the drilling fluid and formation properties. ,, Moreover, the filtrate passed through the filter cake layer has a great impact on the drilled rock characteristics and significantly affected the rock pore structure. ,, …”

“…37,44,48 Moreover, the filtrate passed through the filter cake layer has a great impact on the drilled rock characteristics and significantly affected the rock pore structure. 7,49,50 Furthermore, increasing the solid content of the weighting agent particles in drilling fluid formulation influenced the rheological properties. A sketch behavior of the rheological models for the weighted drilling fluid with a high solid content is complicated owing to numerous factors that essentially need to be considered.…”