Commingle Zubair Shale Sand Sequences by Using Deformable Sealing Polymer in Customized Drilling Fluid, Case Histories from Kuwait

Abstract

Shale stability and differential sticking are the main challenges while drilling through shale and sand sequences. Conventional mud systems cannot always provide the required wellbore stability and sustained high overbalance, which has led to an increase in use of ‘customized fluids’. Offset wells were reviewed to identify the issues while drilling this challenging trajectory through troublesome stressed Zubair shale and sand sequences. This review revealed serious well-bore instability, pack offs, differential stuck pipe leading to the loss of downhole tools and sidetrack operations. Traditionally, oil-based mud (OBM) have been used while drilling these formations with high NPT hours. Due to necessity of comingling two sections in a single section, it was necessary to identify a fluid's solution, which can provide good borehole stability. A customized drilling fluid system was designed by using deformable sealing polymer (DSP, deformable size) in conjunction with Synthetic Resilient Graphite and Sized Calcium Carbonate (CaCO3) in conventional OBM. These Nano particles effectively plug the pore throats and minimized the fluid invasion, which was confirmed by particle / permeability plugging tests under down hole conditions to overcome below challenges. Improve hole stability through stressed shale formationsMinimize risk of differential stuck pipe across low pore pressure formationsMitigate induced losses by utilizing unique wellbore-strengthening techniqueEnhance hole-cleaning efficiency at critical angle Drilling, logging, running and cementing liner was successfully completed in the commingle section without any incident. There was no NPT related to well-bore instability or differential sticking tendency reported. Very low torque and drag was observed in addition to enhanced well-bore cleaning in the high angle section. This paper will present the success of the deformable sealing polymer in OBM utilized to comingle Upper Zubair shale and Ratawi shale with case histories for reference.

Novel Research on CuONPs/MWCNTs Effect on the Properties of Na-Bentonite Water Based Drilling Muds with Experimental Study

“…39,40 Low filtration loss is a characteristic of good drilling mud and the key bore hole integrity. 52 As a result of our study (Fig. 6), it is seen that filtration loss decreases with the increase of CuONPs/ MWCNTs.…”