Effect of fracture network on water injection huff-puff for volume stimulation horizontal wells in tight oil reservoir: Field test and numerical simulation study

Horizontal wells with volume fracturing stimulation technique is an effective technique to improve the single well oil production in tight oil reservoir, in which contact area of wellbore and formation is enlarged and large scale fracture network to improve the conductivity is formed. However, water injection is commonly avoided for fractured reservoirs because of the water channeling problem, which leads to the rapid decline of oil production. Water injection huff-puff is proved to be an effective method to improve the formation pressure and oil production. In the previous studies, researchers pay more attention on the huff-puff well, and the production of adjacent wells and its influencing factors are not taken seriously. Herein, the water injection huff-puff test is carried out in Huanjiang oilfield. Performance of both huff-puff well and adjacent wells are improved with oil production increased by 168.29 m3 and 876.82 m3, respectively. Two effect modes for adjacent wells are summarized considering the fracture network, well position and water breakthrough type. Moreover, reservoir numerical simulation is performed to investigate the influence of fracture network on the performance of water injection huff-puff technique. Two kinds of fracture network models of main fracture-connected model and main fracture-disconnected model are established. The results indicate that fracture network influences the performance of water injection huff-puff. For fracture connected model, shutting down adjacent wells during water injection period is an effective method to improve oil production in the whole field due to the fact that water channeling will occur leading to low formation pressure replenishing efficiency and sharp water cut rising of adjacent wells. For fracture disconnected model, formation pressure near the huff-puff well is significantly improved and so as the oil production. Water displacement effect is obvious for adjacent wells. The oil production of adjacent wells increases obviously without water cut rising sharply. In this model, shutting down adjacent wells during water injection is not recommended considering the long well occupation time.