Research Of Mud Loss Control In Fractured-type Carbonate Reservoir In The Block 10 Of Tahe

The Ordovician reservoir in the block 10 of Tahe Oilfield is a fracture-cavity limestone formation which has strong heterogeneity.Lost circulation caused by the complex fracture network is one of the most important challenges in the drilling of carbonate reservoirs in the block 10 of Tahe.However,the current methods for mud lost circulation control are more for Non-reservoir.So it is necessary to develop a new technology of loss control for Ordovician reservoirs.In this paper,we analysis the lost circulation and crack characteristics of the Ordovician reservoir in the block 10 of Tahe Oilfield.The comprehensive performance of LCMs from the scene and selected manufacturers was evaluated by acid solubility evaluation,temperature resistance evaluation,the particle size distribution analysis,plugging performance evaluation and drilling fluid compatibility analysis.As for micro-fractures,we select three kinds of LCMs to get the formula for plugging while drilling.The lost circulation material blends for plugging while drilling aging at 140?for 16 hours can plug 0?0.5mm cracks until the plugging pressure reach above 7MPa.And the plugging layer has high acid solubility.And the lost circulation materials blends for plugging while drilling has little effect on drilling fluid viscosity,API filtration,lubrication coefficient and filter cake stuck factor.As for small to medium fractures,the particle size distribution of lost circulation material blends is optimized with filtration loss as the evaluation index based on the fracture width.The response surface model is established to relate filtrate of muti-fractures and particle size distribution(PSD)of bridging particls,including response surface design,modeling and optimization.The lost circulation material blends for small to medium fractures aging at140?for 16 hours can plug 0?2.0 mm cracks until the plugging pressure reach above8 MPa.And the plugging layer has high acid solubility.The lost circulation control technique has applied in lateral horizontal well TH10116 CH and successfully prevented loss of drilling fluid in Ordovician carbonates reservoir.