Plastering Effect of Casing Drilling; A Qualitative Analysis of Pipe Size Contribution

Abstract

Casing Drilling is a process in which the well is drilled and cased simultaneously. The original purpose of developing this technology was to eliminate the Non-Productive Time (NPT) associated with tripping out drill pipe and running casing. However, during the early implementation of the technology other benefits were observed while drilling with the casing. In this study the authors explain how these benefits can be related to the larger diameter of the casing compared to drill pipe. The Plastering Effect is an inherent and unique feature of Casing Drilling that strengthens the wellbore, prevents lost circulation, and mitigates formation damage. Plastering Effect augments the pressure containment of the wellbore by smearing the drilling cuttings and available PSD (Particle Size Distribution) into the formation face, hence sealing the pore spaces. This continuous process creates a low porosity, low permeability filter cake on the wellbore wall reducing or preventing losses to the formation and effectively widening the operating mud weight window. In Casing Drilling operations the casing is used to drill the well so the (pipe size/hole size) ratio will be larger than the ratio when conventional drilling pipe is being used. This feature is a significant contributor creating the Plastering Effect. Casing dynamics is qualitatively compared to drill pipe. Pipe ontact angle and area, side force and momentum, and grinding effect, are analyzed to help understand how the benefits of the Plastering Effect are created and answer the question of why it happens in Casing Drilling and not in conventional drilling. Casing Drilling has been used successfully in numerous difficult wells to drill through troublesome well sections which would not have been possible to drill with conventional drill pipe techniques. The Plastering Effect of Casing Drilling has been recognized as an enabling tool to overcome difficult drilling challenges. Therefore, understanding its mechanism is crucial to its successful application.

Evaluation of Annular Pressure Losses while Casing Drilling

“…Plastering effect also enhances the pressure containment of the wellbore by smearing the drill cuttings in to the formation pore spaces. Smaller particle sizes are generated by Casing Drilling operation confirms the smearing effect of the casing string (Karimi et al 2011). During early implementation of the technology, other benefits were seen while drilling with large diameter casing.…”

“…It is intended to perform CFD simulation for selected geometries and fluid properties in order to investigate the effect of geometrical parameters as well as rheological parameters on pressure drop. In fact, successful Casing Drilling operations were reported at radius ratio of κ~0.8 (Karimi et al 2011). Comparison with the evaluated field data is conducted to investigate the role of pipe rotation and eccentricity on pressure losses.…”

Hydraulics and Well Control Complications in Unconventional Shale Laterals

“…Researchers reported that DwC technology showed a 10% reduction in cost and 30% savings in time (Lopez and Bonilla, 2010;Sánchez et al, 2012). Other investigators showed that lost circulation was significantly reduced (Fontenot et al, 2003;Karimi et al, 2011) and stated that fracture gradient and wellbore strengthening were improved (Salehi et al, 2013). Examples of successful field application of DwC technology were published (Aadnoy et al, 2009;Radwan and Karimi, 2011).…”

“…The greater the contact area and the smaller the contact angle, the greater the casing string smoothing effect. When these conditions are coupled with casing side forces and momentum, it potentially fills hole washouts and breakouts(Karimi et al, 2011) Sánchez et al (2012). reported an improvement in the cement operations because of gauged wellbores Salehi et al (2013).…”