Abstract
Fractures and cavities are very well developed in fractured vuggy carbonate reservoirs in Tahe Oilfield, showing obvious constant volume or approximate constant volume characteristics, and the development of karst vuggy reservoirs is characterized by strong randomness, locality, heterogeneity, and discontinuous development, which has a great impact on oilfield development effect. The application of conventional reservoir engineering methods in this kind of reservoir has many limitations. The traditional water injection indication curve is mainly based on a sandstone reservoir, ignoring the elastic energy of the water body in a reservoir and the combination relationship of fracture and cavity, which can not meet the needs of the carbonate reservoir. According to the principle of volume balance of constant volume body and considering the elastic energy of original formation water, a new model of improved water injection indication curve and the original water-oil ratio of carbonate reservoir is proposed, and the chart of water injection indication curve is established. Compared with other methods, this method has the advantages of low cost and accurate identification results. The calculated reservoir parameters such as single well-controlled reserves, well-controlled water volume, and original water-oil ratio have high reliability, and the chart is easy to use. The model is applied to the Yuejin block of Tahe Oilfield, and the results show that the improved model is consistent with the results of other test methods, such as high-precision seismic combined with fracture cavity carving technology, which indicates that the model has strong reliability.
Highlights
There have been many discussions on the characteristics and uses of the water injection indicator curve in the carbonate reservoir, but the theoretical research on the water injection indicator curve model in this kind of reservoir is relatively rare or has not formed a unified understanding [1–5]
To fully understand and utilize the data in the process of water injection in the carbonate reservoir, analyze the oil-water relationship in the reservoir, and correctly guide the implementation of the working system and measures, the author takes the unsaturated carbonate reservoir as an example to study the establishment of reservoir water injection indicator curve model, the drawing of curve line, and its application, to provide the selection of water injection volume in the process of oil displacement by water injection, the water injection indicator curve will play a better role in the development of carbonate reservoir in the future
The carbonate reservoir is different from the sandstone reservoir
Summary
There have been many discussions on the characteristics and uses of the water injection indicator curve in the carbonate reservoir, but the theoretical research on the water injection indicator curve model in this kind of reservoir is relatively rare or has not formed a unified understanding [1–5]. Ma and Mei et al derived the modified water injection indication curve considering that the elastic energy of Geofluids original formation water in the fractured vuggy reservoir can not be ignored: (1) the theoretical model is not combined with the actual needs of the site; (2) the theoretical model ignores the calculation of the original water-oil ratio R in the actual use process. In this case, the relative error can be reduced to 0, which lacks practical use value [17, 18]. The expression of the original water-oil ratio R is added into the new model to determine the volume of crude oil and formation water in the cave constant volume body more accurately
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