Cementing technology of Ø244.5 mm technical casing and high-density cement slurry in Well Mingbulak 15

The Fergana Basin of Uzbekistan is characterized by high temperature, high pressure, high salt content, high sulfur content and narrow formation pressure window, and Well Mingbulak 15 is one important deep exploration well of Mingbulak Oil Field in the Fergana Basin. The data of its neighboring well show that in this block, the oil reservoir is deep, the formation temperature is high, the formation pressure above the oil reservoir varies greatly, there are several high-pressure saline aquifers and low-pressure thief zones and the actual safety density window of drilling fluid is only 0.02 g/cm³, which result in high cementing accident rate and poor cementing quality. In order to improve the cementing quality and reduce the drilling risk in the oil layer of the fourth section of Well Ming 15, Ø244.5 mm technical casing was used in the third section for the cementation to the top of the oil layer in the full hole, i.e. 0-5 177 m. The “binary grading” combination of jacobsite and hematite was selected, and combined with novel polymer crosslinking anti-channeling agent and large temperature difference retardant, the slurry system of high density (2.35 g/cm³ and 2.45 g/cm³), high temperature resistance, salt resistance and channeling prevention was formed. The large-casing staged cementing of deep well was applied to reduce the cementing construction and lost circulation risks for the first time. The wall shear force of cement slurry and spacer fluid were adjusted into the range of 15-30 MPa according to the principle of wall shear with low return velocity, and thus high displacement efficiency at low return velocity was realized in the deep well. The qualification rate and high quality rate of the cementing in the third section of Well Ming 15 are 80 % and 48 %, respectively, which are the highest level in this block. The successful application of this cementing technology provides valuable successful experience for the cementing in the layers with high density, high temperature and high and low pressure in Ming and other blocks.