A Study of High Performance Drilling Mud Used in the Southern Margin of Junggar Basin

The southern margin of the Junggar Basin is composed of four strata known as Taxihe (N(1)t), Shawan (E(N1)s), Anjihaihe (E(2-3)a) and Zibiqunzi (E1-2Z) formation which are complex crushing zones and also vectors of drilling accidents such as reduction of drilling rate, differential pipe sticking and well leakage. Based on the core mineral composition, potassium calcium-based organic salt drilling mud (PCS), potassium calcium-based polysulfonate drilling mud (PCP), and organic-salt polyalcohol drilling mud (OSP) were the mud systems selected for the drilling process and their performance were compared. The four strata exhibited a clay mineral content of 29.9% with an Illite/Smectite mixed layer content above 75% as well as an inter-layer average ratio of 45%. Moreover, the drilled cuttings satisfactory dispersed and expanded in the mud systems. Furthermore, among the three drilling mud systems, OSP demonstrated favorable tolerance to calcium electrolytes contamination with a appreciable drilled cuttings tolerance as well as a remarkable sealing performance. Hence, translating its suitability to be used to drill the mudstone formation in the southern margin of the Junggar Basin.