Activity in the Ordos Basin, China, has mostly occurred in the low-permeability, clay-rich Chang 7 sandstone, and has used multifractured horizontal wells as the preferred completion technique. To improve further the production potential and to increase operational efficiency, a dual-well pad site was engineered to try a pad-drilling approach and to evaluate different completion techniques, use integrated work flows, and accelerate the development cycle.
The pilot project involved two pads with two horizontal wells each, with the intention to compare the local multistage stimulation practice of using a tubing-conveyed completion method to a wireline-conveyed plug-and-perforation technique. The current tubing-conveyed completion practice affects the completion efficiency of the well from the standpoints of surface efficiency, engineering work flow, post-fracturing performance, and subsequent commercial performance. The wells completed with the plug-and-perforation technique were completed in a shorter period of time; simultaneous operations enabled flowback water from the first well to be recycled and reused on pumping operations on the second well, further improving the project performance, and first-year cumulative production was 20% higher compared with surrounding offsets.
Three vertical wells were placed between the parallel horizontal wells to enable real-time fracturing monitoring and to improve subsurface understanding. To have a more-precise microseismic mapping result, the closest vertical well was selected as the monitoring well.
The study demonstrates the importance of an integrated approach that accounts for well design, engineering work flow, technology used during the execution, and subsequent evaluation while improving overall productivity. Both the efficiency and the production result were breakthroughs in this area.