Dynamic description technology for fracture-vug carbonate reservoirs based on node network model
The heterogeneity of fracture-vug carbonate reservoirs is extremely strong with discretely distributed fracture-vug bodies,and the static description based on geophysical description techniques is highly uncertain.Dynamic description techniques make use of dynamic data to deepen the understanding of reservoirs,which is an important way to improve the precision of reservoir description by combining dynamic and static techniques.Most of the existing dynamic description techniques are mainly established based on the continuum theory,which is difficult to reflect the discrete distribution characteristics of fracture-vug bodies,and have poor"compati-bility"with geophysical carving results.A dynamic description technique based on node network model was created based on the dis-crete distribution characteristics of fracture-vug bodies.Firstly,a discrete fracture-vug characterization method based on node net-work is proposed,and an automatic generation method of node network model is also established,aiming to realize the rapid trans-formation between the geophysical carving model and the node network model;secondly,a flow characterization and development in-dex calculation method is built based on the node network model.Calculation examples show that the goodness of fit for the calcula-tion results of development indexes such as production and pressure is over 93％,and the calculation speed is increased by 156 times;finally,an inversion method for the key characteristic parameters of fracture and vug is established,and 7 key characteristic parame-ters for fracture-vug reservoirs,including 3 in Class Ⅰ and 4 in Class Ⅱ,are defined.Based on Latin hypercube sampling,the paper establishes an auxiliary historical fitting method,determines the probability distribution of key characteristic parameters of fracture and vug,and develops software modules.Calculation examples show that the inversion errors for the reserve of fracture-vug bodies,volume of water bodies,and fracture permeability are all about 10％,which met the requirements of dynamic analysis.The technolo-gy has been validated and applied in multiple units(well areas)of Tahe oilfield,and the historical fitting coincidence rate for develop-ment indexes can reach more than 90％,which has realized the quantitative characterization of geological reserves and production de-gree of fracture-vug bodies,and improved the pertinence and effectiveness of development measures.
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