Novel Approach for Lost Circulation Treatment While Drilling with an MPD System by Using a Combined High-Strength, Pressure-Activated and Thixotropic Swelling Polymers

Abstract

This paper is a study on a novel approach for specialized lost circulation treatment while drilling with a managed pressure drilling (MPD) system through weak and over-pressurized zones where high density water-based drilling fluids are required. These weak zones are characterized by natural and induced fractures. This study includes a review of different lost circulation scenarios encountered while drilling, a root cause analysis of these losses and the successful applications of this novel high-strength, pressure-activated, high-solids lost circulation material (LCM) pill combined with a unique thixotropic swelling polymer pill. The combination pill was applied in a high pressure, high-temperature (HPHT) environment where conventional LCM could not stop the losses or minimize the losses. This new technique uses two pills pumped in tandem, a swelling polymer pill followed by a high-strength pressure-activated pill. The technique involves mixing, pumping, spotting and squeezing procedures while the wellbore was pressurized via the annulus. It resulted in the total treatment of the losses as well as strengthening of the formation to being able to withstand 2 pcf of additional equivalent mud weight (EMW) to its in-situ fracture pressure limit. Meanwhile, other conventional lost circulation treatment techniques and products only resulted in a temporary fix of the lost circulation and the wellbore eventually broke down again after drilling resumed. This occurred because the LCM did not remain in the fractures and was eventually removed from the wellbore. This new technique is safe, reliable and reduces the frequency and likelihood of formation influx and losses. It ultimately improves crossflow management and minimizes non-productive time associated with lost circulation. This paper will discuss different lost circulation scenarios, and the successful application of the high-strength, pressure-activated, high-solid squeeze and thixotropic swelling polymer solutions. It will also highlight the formation lithology and characteristics of the lost circulation zone as well as illustrate the operational sequence for spotting this specialized lost circulation treatment.