The Effect of Nano Drilling Fluids on Reduction of Clay Swelling

Abstract

Shales make up about three fourths of drilled formation and over 90% of the wellbore instability problems that occur in shales. Even though shale stability has been studied for several decades, it still a serious problem in not only the petroleum industry but also in the mining and construction industries. Before any measures are taken to address this problem, it is crucial that potentially problematic formations and the mechanisms of wellbore instability be identified. Once the mechanisms are understood, well planning, drilling fluid design, and drilling operation strategies can be implemented to ensure wellbore stability. Due to the unique mechanical and physicochemical properties of shales, it is wellrecognized that wellbore instability in shales is a complicated problem. Shale cuttings consisting of different montmorillonite content were collected from four different wells in Sinai. They were evaluated using X-ray diffraction (XRD), X-ray fluorescence (XRF) and cation exchange capacity (CEC) using Methylene Blue (MB), hence classified into shale 1, 2 ,3 and 4. Swelling index of the shale measured using compressed disks of shale in contact with OCMA bentonite for 20 hrs using the Linear Swell Meter (LSM). Nanoparticles in terms of CuO, Graphene nanoplatelets and SiO2 used as an inhibitor of swelling of shale cuttings. The inhibitors are added to OCMA bentonite as well. Swelling of the shale directly related to montmorillonite content, more montmorillonite means more swelling in contact with OCMA bentonite. The inhibition of swelling of these shale cuttings using KCl achieved a decrease in swelling that ranged from 15% at 7% (shale 1), 14% at 6% (shale 2), 14% at 4% (shale 3) and 17% at 9% (shale 4). with estimates over $1 billion in annual cost to the industry. Preventing shale instability is a high priority to every phase of the drilling fluids industry, from research and development efforts to field implementation by the mud engineers. New technolIntroduction Maintaining a stable wellbore is one of the major challenges when drilling a well. Studies indicate that, unscheduled events relating to wellbore instability account for more than 10% of well costs, • Page 2 of 17 • Noah et al. Int J Nanoparticles Nanotech 2019, 5:024 ISSN: 2631-5084 | Citation: Noah AZ, El-Khadragy AA, Ramadan FS, Mohamed MI (2019) The Effect of Nano Drilling Fluids on Reduction of Clay Swelling. Int J Nanoparticles Nanotech 5:024 ogies are continually being developed and applied and earlier technologies refined. Shale causes world’s 70% of wellbore instability problems. Shale instability is caused due to the presence of clay minerals into the shale. These clay minerals in particular kaolinite, smectite and montrolite have great affinity with the water. However, clay minerals start to swell after they interact with the water because of the special behavior of the clays is due to their unique structures. The crystal structure of swelling clays consists of Al-OH or Fe-OH or Mg-OH octahedral, sandwiched by two Si-O tetrahedral layers. These layers are always deficient in positive charges because of cation substitution. Interlayer cations are required to balance the negative layer charges. When the exchangeable cations are hydrated during water injection and water molecules enter the space between the structure layers, the distance between the two layers increases leading to clay swelling. And as a result, clay swelling raised the wellbore instability such as shale sloughing, tight hole, caving and reduce efficiency of mud to lift the drilled cuttings. Clay swelling reduces the rate of penetration (ROP) due to bit balling with sticky clay.