3D Fracturing Network Optimization Techniques for Horizontal Wells in Sandstone-Conglomerate Formations

Block Yan 227 is a thick tight sandstone-conglomerate reservoir with ultra low permeability.The result of fracturing in a conventional vertical well was too poor to obtain a satisfactory yield,to the point that it is even not desirable to develop such a thick reservoir with a single horizontal well.Based on the concept of factory production from numerous countries for shale gas,a three-layer development model was developed.The model included a group of eight horizontal wells for fracturing:three wells were included in the first layer,another three wells in the second layer,and remaining two wells in the third layer.The length of the horizontal section ranged from 900 to 1 400 m,the vertical span in the three layers was 80 m.Fracture parameter matching was done with wells within the same layer as well as between layers to establish a 3-D fracture network to improve the controlling degree of reserves.Operating parameters were optimized,with a new type of real-time mixing technology for fracture fluids,which included pumping a bridge plug for staged fracturing,and monitoring fractures in real time,which allowed eight wells in four well groups with 87 sections to be fractured.The fracture monitoring results showed that a 3D fracture network was formed.The centralized multi-well fracturing technology has many advantages compared with single horizontal well fracturing,including the fact that average operation cycle time was shortened by 50%,and the production cost of a single well was reduced by 3.955 million RMB.After treatment,average daily oil production of single well was 11.8 t/d,which was four times higher than that in the vertical well in the same block.It is a good experiment for economic recovery in similar tight oil reservoirs.