T Oilfield Carbonate Reservoirs

T oilfield is a ordovician slope break belt reef facies limestone reservoir. Horizontal wells are commonly used for exploitation. Because of low reservoir permeability, strong heterogeneity and limited precision rate of geophysical technology, making acid fracturing a necessary step to obtain production. There are already42acid fracked wells by now, However, Early acid fracturing measures are found to be great variation in stimulation effect and low in efficient, such as the Lianglitake formation yield better production than Yingshan formation. Thus comprehensive evaluation to acid fracturing performance is needed to improve effective rate afterward, deepen the recognition of reservoir condition and formulate countermeasures for different types of reservoir, directing high efficiency acid fracturing.This paper focuses on the research of the acid fracture conductivity, performance assessment of pressure controlled screen ball segmentation technology and comprehensive effect evaluation of acid fracturing based on the data analysis of previous acid fracturing treatment with a technological mean combined statistical analysis, laboratory experiment and theoretical simulation. The following achievements and recognitions can be obtained:(1) Geological and engineering factors affecting acid fracturing performance were analyzed comprehensively based on the production rate after treatment. The results showed that reservoir quality was the key to success acid fracturing and the appropriate technology was an important way to insure the effect of fracturing.(2) Combined macro experiment (acid rock reaction ability evaluation, acid fracture conductivity measurement) and microscopic analysis such as X-ray diffraction, energy spectrum analysis, laser scanning and ultrasonic scanning, the effect of the heterogeneity of rock plate, types of acid fracturing technology, acid concentration, acid type under tensile crack, surface morphology and closed acidizing on conductivity were studied comprehensively from different aspects. The quantitative relationship between etching morphology and flow conductivity was established.(3) According to the process principle of pressure controlled screen ball segmentation technology, combined with the movement rule of ball sealer, force analysis before and after setting, and multi-ball sealing at the same time, multi-ball sealing model was established appropriate for the targeted oilfield. The sealing performance was evaluated combined with response of field treatment curve. The research results showed that multi-screen can be opened at the same time. Once the multi-screen was opened simultaneously, there would be a repeated fracturing in the same section, which would significantly reduce the acid fracturing effect.(4) BP neural network was used to establish the filter model of influence factor of acid fracturing performance on the basis of grey correlation and partial correlation analysis. The main factors affecting the effects of acid fracturing was screened out, and the recommended acid fracturing scheme suitable for different reservoir condition was given combined with statistical regularity of acid fracturing results, laboratory experiment and evaluation results of segmentation effect with subsection technologies.The research content and achievements obtained in this paper can enrich and perfect the acid fracturing effect assessment for horizontal wells in T oilfield, which has certain certain theoretical value and practical significance, and in the meanwhile, what have achieved in this paper can further develop the acid fracturing effect evaluation technology for carbonate horizontal wells, and provides reference for the research methods and technical ideas.