Mitigation of Stuck Pipe Challenges in HTHP conditions Using Acid Soluble Blend of Barite and Manganese Tetroxide as Weighting Materials for Drilling Fluids

Abstract

Abstract Horizontal wells drilled in the Marrat (lower Jurassic), Minjur and Jilh (upper and middle Triassic) formation in Saudi Arabia are known to present severe stuck-pipe challenges. Stuck pipe in a horizontal well is a problem that can result in loss of tools, non-productive time, sidetracks and loss of well thereby increasing the wellbore construction cost. Thus to mitigate the problems arising due to stuck-pipe issues, a new drilling fluid was formulated using a combination of barite and manganese tetroxide (Mn3O4) as weighting agents. The use of such a combination as a weighting material in a drilling fluid provides both operational and monetary benefits. Mn3O4 with a smaller particle size (D50=1 µm), spherical shape, and high specific gravity (4.95 g/cm3) makes it a good weighting material to reduce solids loading and settling compared to barite (SG= 4.20 and D50=20 µm). The fact that manganese tetroxide is also acid-soluble provides more operational benefits when a fluid with a combination of barite and Mn3O4 is used as weighting agent. In the event of a stuck-pipe incident during drilling, the use of acids or acid precursors would result in the dissolution of the Mn3O4 thereby resulting in a partial breakage of the manganese tetroxide-barite filter cake formed in a well during drilling. This partial breakage of the filter cake is expected to free the pipe thereby mitigating the problems associated with stuck pipe incidents. The use of a barite along with Mn3O4 would also result in a reduced fluid cost as compared to a fluid formulated with Mn3O4 alone as the weighting agent. Thus, this paper showcases the benefits of using such a combination of barite and manganese tetroxide as weighting materials in 100pcf, 120pcf and 150pcf drilling fluids hot rolled at 250°F/300°F. The experimental work in this paper involves measuring rheological properties, thermal stability, HTHP filtration and static sagging resistance of the fluid at 250°F/300°F. The paper also describes the results of using different acid based filter-cake breaker fluids for the partial dissolution of manganese tetroxide based filter cake. A blend of manganese tetroxide and barite provides increased sag resistance as compared to a drilling fluid formulated with barite alone as the weighting agent.