Experimental Study on Tanuma Shale Stability Using Drilling Fluids with Different Additives

Abstract

Shale formation is represented as one of the challenge formations during drilling wells because it is a strong potential for wellbore instability. Tanuma formation in Iraqi oil fields (North Rumila) is located at a depth from 2102 m MD – 2126 m MD. It is considered one of the most problematic formations through drilling wells in North Rumila. Most problems of Tanuma shale are sloughing, swelling, caving, cementing problem and casing landing problem caused by the interaction of drilling fluid with the formation. This paper focuses on studying the chemical and minerals properties of Tanuma shale. In addition, study the effect of drilling fluids and additive salts by using different techniques; (XRD, XRF, reflected and transmitted microscope, scanning electron microscope and EDS)Also, the study includes experiments to observe and enhance the shale stability by using two types of drilling fluids, API and polymer type, with different additives. Four types of additives (KCl, NaCl, CaCl2 and Sodium silicate) in different concentrations (0.5, 1, 5 and 10) wt % and different immersion period (1, 24 and 72 hours) were used. The results show that adding 10 wt. % of sodium silicate to API drilling fluid results in a high percentage of shale recovery (77.99%). While, the maximum shale recovery was (79.76%) in polymer drilling fluid type gained by adding 10 wt % of sodium silicate.