Productivity Evaluation Of Horizontal Well And High Deviation Well In Changxing Formation Of YB Gas Field

Changxing Formation of YB gas reservoir is divided into reef and beach facies, this lithologic gas reservoir is character by high hydrogen sulfide, medium carbon dioxide, ultra-deep, crack-pore, local presence of edge (bottom) aquifer and reef body control.Because H2S gas is highly corrosive and toxic,"more production with fewer wells" is always taken as a development guideline. Horizontal wells and highly deviated wells are always implemented in these kinds of reservoirs. In sour gas reservoirs, testing time is shorter and capacity analysis is more difficulty; Productivity evaluation of horizontal wells is also different from the general gas reservoir. In the development of a new block, productivity evaluation and development strategy can provide rational and scientific basis for the development of YB gas reservoir, it also has great significance for the long-term exploitation of the block. This paper mainly study productivity evaluation of horizontal wells and highly deviated wells of YB blocks,it has been done based on gas reservoir engineering and fluid mechanics, using Eclipse. Following findings have made:1)Unstable test interpretation of12wells of YB gas reservoir is conducted, and evaluation of capacity for26wells is calculated using various "one point method", a binomial, exponential approach is used to calculate qAOF from system test. A "one point method" of this block (a=0.13) is established. A relationship between qAOF and well test Kh and log Kh of reef, beach by regression.2) The mechanistic model of single well with highly deviated wells horizontal wells is established, a sensitivity analysis of factors that influence production capacity is made, while stable production time and cumulative production are taken as criteria. These factors include horizontal permeability, skin factor, horizontal length/angle of inclination, formation heterogeneity, side (bottom) aquifer.3) On the basis of well productivity evaluation, the critical carrying fluid flow method, critical carrying sulfur method, erosion flow method, prc-production method, gas wells IPR curve method were used to determine appropriate production rate. For the highly deviated wells, horizontal wells,1/8,1/9of qAOF is taken as the principle of initial production rate, and for wells having no test data, analogy method was used to determine production rate, on the basis of relationship between qAOF and Kh.4) A3D geological model was built. The results of the well test interpretation were used to calibrate permeability. Effect of side (bottom) aquifer on well production potential is studied by full filed model. Production capacity of14wells in pre-production area,23wells in sequential developing area is analyzed.