Progress of research on productivity forecasting formula for radial multi-lateral horizontal wells
Abstract: The paper presents a systematic summary of the origin and developmental process of research work on productivity forecasting of radial multi-lateral horizontal wells. It is recognized that the productivity forecasting formula of radial multi-lateral horizontal wells in a circular horizontal edge-water-driven reservoir derived by Qi Chengwei (hereinafter referred to as Circular-Radial-Formula) is the most effective one to date. It is shown from the degeneration relations between productivity formulae that, if the spacing between production segments is zero, Circular-Radial-Formula degenerates rigorously to Jiang Tingxue formula, or approximately to Cheng Linsong formula; and if there is only one production segment, Circular-Radial-Formula degenerates rigorously to Giger formula, or approximately to Борисов formula. Through simulation of flow with the current, the flow field in porous media excited by a radial multi-lateral horizontal well can be measured. It is known from the simulation that, the productivity–parameter relationship implied in the Circular-Radial-Formula is consistent with experimental results, with an accuracy that satisfies engineering requirements; the prediction accuracy is inversely proportional to the number, length, radial distance and eccentricity of production segments. To facilitate the application of the Circular-Radial-Formula to the design of well structure and parameter optimization of a radial multi-lateral horizontal well, two new concepts are proposed: hole enlargement ratio and productivity ratio, design charts are plotted based on the functional relation between hole enlargement ratio and productivity ratio. Lastly, the future direction of research work is pointed out.
Key words: mechanics of fluids in porous media; well with complicated structure; productivity prediction; Qi Chengwei formulae; simulation of flow with the current; accuracy analysis; well completion optimization
Progress in Productivity Formulae of Branched Horizontal Wells in Ribbon-Shaped Reservoir
Abstract: After systematic examination of the origin and evolution of research on productivity forecasting in branched horizontal wells in ribbon-shaped oil and gas reservoirs, it has been recognized that QI-Chengwei’s productivity prediction formulae for transverse and longitudinal bilateral horizontal wells in ribbon-shaped reservoirs (hereinafter referred to as “ribbon-transverse-formula” and “ribbon-longitudinal-formula”) are the most effective ones to date for several reasons. Firstly, the “ribbon-transverse-formula” is effective in cases of short well distance where Меркупов’s formula does not work. Secondly, sandstone seepage experiments by SHEN-Rui et al from Porous Flow and Fluid Mechanics Institute of Chinese Academy of Science confirmed the validity of degenerate version of ribbon-transverse-formula in cases where the production section runs through the width of the ribbon-shaped oil reservoir. Thirdly, analyses are presented of differences between the degenerate version of ribbon-transverse-formula and SHEN-Rui’s forecasting formula and causes of error in the latter. Fourthly, water-electricity simulation experiments confirmed that forecasting accuracy of ribbon-transverse-formula and ribbon-longitudinal-formula satisfies engineering requirements. By way of conclusion, a system of productivity forecasting formulae is proposed and suggestions are made for future research.
Key Words: fluid flow in porous media; complex structure wells; productivity prediction; QI Cheng-wei’s formulae; flow-current similar experiment; accuracy analysis
