Sparse well pattern and high-efficient development of metamorphic buried hills reservoirs in Bohai Sea area, China

Abstract

In order to achieve the development objective of fewer wells with higher production of metamorphic buried hill reservoirs in the Bohai Sea area, the JZ251S oilfield at Bohai Bay Basin was taken as an example to carry out elaboration of reservoir fracture, quantitative characterization of water displacing oil mechanism at dual-porosity reservoir, optimization of new well pattern mode, formulation of rational development technology policy, maintaining productivity and controlling water rising based on development experience of similar oil reservoir, thus forming the key high efficiency development technique of sparse well pattern of offshore metamorphic rock reservoir. Based on the characteristics of the JZ251S buried hill reservoir, forward simulation of wave equation for fracture anisotropy was carried out, verifying the effectiveness of narrow azimuth seismic data to fractures detection in work area. Multi-parameters prestack inversion and geostress field simulation were applied to forecast location of fractures and direction of fractures respectively. Based on the large-scale 3D physical model and numerical simulation, a new top-bottom interlaced 3D injection-production well deployment model concerning the horizontal well was presented. Considering the production demand, the reasonable oil production rate of JZ251S oil reservoir shall be controlled at 3%-4%, depletion development until that the formation pressure level maintains at 70% of initial formation pressure can be implemented for the oil field at the initial stage, and then the development mode of water flooding to keep pressure can be carried out. Considering the pilot production data at the work zone, different water breakthrough models of the horizontal well were simulated to form four diagnosis charts, which help to stabilize oil and control water effectively. The field practice shows that these techniques greatly increase the crude oil output and improve the water-injection development effect. Key words: Bohai Sea area, metamorphic buried hill, buried reservoir, fracture forecast, well deployment model, reservoir development techniques, maintaining productivity and controlling water rising