Inter-fracture asynchronous periodic injection-production energy supplement technology for horizontal wells in ultra-low permeability reservoirs

Since horizontal wells in ultra-low permeability sandstone reservoirs lack effective means of energy supplement, an alternate injection-production process between fractures in same horizontal well was proposed. The process string is composed of release sub, Y445 packer, Y341 packer, one-way injection dispenser, one-way production dispenser, and card stripper, which can realize water injection in partial fractures and oil production in other partial fractures. Therefore, the staged asynchronous injection-production energy supplement can be realized in a same horizontal well. Asynchronous injection-production and oil-increasing between fractures is the result of the combined action of multiple driving mechanisms, including water flooding, elastic flooding, and imbibition. Compared with the traditional area water injection well pattern, it is easier to achieve more effective flooding effect. The research shows that: for the inter-fracture asynchronous periodic injection-production energy supplement method in the same well, the water in injected in to the hydraulic fracturing fractures, which greatly increases the water absorption area in the reservoir; the shape of the flow field changes from radial flow to linear flow; the distance between the injection end and the production end is shortened, which increases displacement pressure gradient and effective permeability. The combined effect of these mechanisms plays an important role in increasing oil production. Field tests show that the inter-fracture asynchronous periodic injection-production energy supplement method in same horizontal well can effectively improve single-well production, and can be popularized to ultra-low permeability sandstone reservoirs on a large scale.