Successful Use of a Synthetic Drilling Fluid in Eastern Venezuela

Abstract

AbstractIncreased drilling performance and low mud consumption rates have made it economical to drill with an environmentally responsible, synthetic drilling fluid in the Orinoco River Delta, Eastern Venezuela. Initially, water based muds were used. Troublesome shales and claystones, coupled with complex tectonic stresses, were cause for numerous hole cleaning and wellbore instability incidents. It was decided to utilize an invert mud with the knowledge that this would inhibit the swelling mechanism of shales and reduce the hydraulic invasion of filtrate into the shale. A synthetic system was chosen for environmental impact concerns, even though the rigs were operating at zero discharge of drilling wastes.This paper details the reasons for the use of a synthetic based drilling fluid and discusses the planning and implementation of the enhanced drilling fluid programme which ultimately led to a step change in drilling performance. The paper also discusses the utilisation of an Alliance Team and the various Alliance networks to deliver solutions to the challenges faced.The results have been excellent: zero spills, improved drilling performance and world class consumption rates. Hole stability has greatly improved with mud densities identical to those previously used for near vertical wells. Since introduction of synthetic fluids, mud density profiles are designed relative to balancing pore pressures, as the rock/water base drilling fluid chemical interaction factor has been reduced.The benefits to operations have been faster completion of wells, lower drilling costs and the ability to plan and operate increasingly difficult wells to better meet demands for production.