Semi-analytical model-based research on influencing factors of the spacing of volume fracturing horizontal well in tight oil reservoirs via consideration of imbibition

Abstract

A mathematical model was established for porous flow of horizontal wells based on the dual-porosity model under consideration of imbibition, which was solved by means of a semi-analytical method to forecast production of multiple wells. Moreover, analysis was carried out to effects of production by those factors such as reservoir energy, abundance (the content of crude oil per unit area of the reservoir), brittleness (the property that the material will break after only producing a small deformation under the action of external force) and well spacing by taking Chang 7 reservoir of ChangQing(CQ) Oil Field (a typical tight oil region in China) as an example. On this basis, an optimal method for spacing of volume fracturing horizontal well in tight oil reservoir was formed under constraints of economic benefits. Our finding indicates that there would be no any optimal well spacing without considering constraints but those factors such as reservoir energy, abundance, brittleness would influence well spacing to bring about parameter optimization considering constraints. As for a complex fracturing area gathered near the wellbore whose reservoir energy, abundance and brittleness are higher, horizontal wells for volume fracturing of tight oil reservoirs shall be distributed in a small well spacing. Additionally, comparison of ChangQing and North American Bakken tight oil reservoirs indicates that the former has lower abundance, reservoir energy and brittleness. While the oil price is $60/barrel, the horizontal well is 1000m long and the well spacing is 400m, the target rate of return can be achievable in tight oil reservoir of CQ Oil Field. However, in case of considering the imbibition, the gain can be obtained while the well spacing is 300m. Our study for optimization of the horizontal well spacing for volume fracturing of tight oil reservoirs provides not only theoretical supports for the porous flow mechanism of tight oil reservoirs but also corresponding technical guidance for petroleum engineers when deploying well patterns.