Study On Failure Control Of Water Injection For Oil Well In Fractured Cavern Type Carbonate Reservoir

Tahe carbonate reservoir is formed by a long period of tectogenesis and ancient karst, which is mainly controlled by karst fracture-cave pools. While, carbonate reservoir is a special and complex type of reservoirs with quite random storage and infiltration space composed of size ranging caves, corrosion holes, fracture and microfissures. Field has implemented the technique water-flooding huff and puff in2005with single well aimed at closed constant volume fracture-cavern block units whose energy is limilted so that oil producing capacity drops quickly, increasing recovery of single wells by an average of2.4%. The effective treatment is imminent as the water injection development has gradually entered the low-effectivity/failure section. In this paper, based on liquid flow mechanism, qualitative evaluation indexes for failure wells and injection indicating curve model for quantitatively analyzing remaining reserves have been proposed. At last, the well failure reasons are summarized and for different indicating curve type different potential tapping measures and treating standards for low-effect water-flooding huff and puff wells have been established.First of all, combining the specificity of carbonate rock and the particularity of reservoir fluids flow, a new coupled hydrodynamic model by utilizing the tubing flow theory and knowledge of seepage is put forth in this paper.Secondly, in order to determine the water-flooding huff and puff wells have been into low-effect stage or not, the evaluation indexes have been proposed including periodic water cut, periodic tempo, periodic water storage rate, periodic injection-production ratio, periodic water consumption rate for a ton of oil and other parameters which can preliminary judge the current effect of water injection wells qualitatively.Besides, carbonate rock injection indicating curve theory has been analyzed and a new single cave reservoir model has been derived. Compared to the original model, the new one has considered the elastic energy of water, appearing a better using effect. The remaining reserves of closed constant cave can be calculated, which, in some degree, can compensate for the lack of qualitative judgment of evaluation indexes.Finally, it has conducted research on a certain typical failure single well, summarized failure reasons and built taping measures and treating standards for failure wells.