Rheological Hierarchy Optimization Improves Fluid Displacement and Well Integrity, 3 Worldwide Case Studies

Abstract

Abstract A good cement job is the Achilles' heel of sustainable production from oil and gas wells. Improving zonal isolation and the integrity of wells worldwide is the priority of well integrity engineers. Proper cement designs and job execution assure sustainable production with ideal zonal isolation. The US unconventional horizontal well drilling has been increasing over the recent years. There are several solutions and best practices including maintaining the rheological and friction pressure hierarchy of the fluids pumped. Spacer rheological properties modeling computer simulations lead to a smart spacer design and, if correctly executed, yield enhanced fluids displacement efficiency and well integrity. The objective of this paper is to demonstrate the benefits of rheological hierarchy optimization and explain the benefits of the execution of this concept in three case studies worldwide. A predictive rheological model was developed for a micro-emulsion weighted spacer technology which was pumped in these cases. In the horizontal section of a well and during fluid displacement, density hierarchy would not prevent fluid intermixing and viscous fingering hence to improve the fluid displacement efficiency a rheological hierarchy optimization is essential. This study showcases how by engineering the rheological properties of a spacer fluid the friction pressure Hierarchy in the horizontal section (liner and long strings casings) was designed. Adjusting the proper spacer's viscosifier and surfactant and being able to predict the rheological properties is another key to achieve zonal isolation. A sensitivity analysis was performred with the inhouse cement displacement simulators and fluid compatibility tests were completed in the laboratory. Results presented by the in-house simulators with three dimensional (3D) visualization and bond logs confirm how engineering, planning and optimizing the rheological and friction pressure hierarchy could achieve zonal isolation.