Applications of Pozzolans to Treat Wellbore prior to Cement, Casing and While Drilling to Prevent Overburden Stress Fractures, Onshore US, Offshore Deepwater, and International Case Studies

Abstract

This study is focused on the application of novel pozzolans (superplasticizers) ahead of cement, prior to casing and while drilling to treat and prevent wellbore fracture due to overburden stresses. This study is a combination of quantitative and qualitative analysis based on laboratory and field applications of pozzolanic materials in the construction of wells. Pozzolans have long been applied to construction materials in order to improve lifespan and compressive strength. The application of pozzolanic materials goes back over 2000 years to the construction of Roman Aqueducts, buildings and roads known for their longevity and ability to resist corrosion and stress. These materials cover a broad range of naturally occurring and man-made materials. The most common pozzolanic materials used in drilling today include Bentonite, Kaolin, and Fly Ash. Pozzolans when combined with Portland Cement have been shown to increase the compressive strength and durability dramatically. Pozzolans are currently applied globally in cementing applications for HTHP, high loss zones and more. This paper will examine the application in the drilling phase as an applied treatment during drilling for the reinforcement of the wellbore as well as to treat induced losses. The study will review cases for use of Novel Pozzolans for drilling, pre-cement, casing and for production zones the application of Novel acid soluble pozzolans for similar purposes. These applications validate the application of these materials beyond cementing into the drilling phase and wellbore construction for reducing backside pressure, reducing days on losses, reducing sidetrack, increasing operational ECD while drilling and cementing and achieving top of cement without inducing losses due to overburden in tight ECD window environments. Deepwater environments provide a unique environment for the application of these novel materials as they offer some of the highest overburden environments with greatest operating costs and daily operating costs. Thusly this study has shown the applications have saved operators on multiple wells and over long periods many days and millions in operating costs with proven prevention of losses in field studies where wells were compared for offset value over a period of time. Multiple operators have adopted this technology as a result and there is a long track record of use while there are few papers on the subject. The purpose of this paper is to illustrate the best practices as well as new technologies and state of the art when it comes to the development of the latest in pozzolanics for these applications.