Though the drainage area of horizontal reservoirs is increased with increase in horizontal well length, construction costs for drilling and completion also increase; this combines with other factors to negatively affect the overall economics of the horizontal well. However, no reliable standards are currently available that take into account the factors necessary for the determination of optimum well length for horizontal drilling.

This paper presents a methodology developed to obtain the optimum horizontal well length based on total economics as well as productivity index (PI) change associated with frictional loss effects in the long section of the horizontal wellbore. An integrated approach is proposed for quantitative analysis of the parameters affecting productivity and economics in order to achieve the overall optimum performance of a horizontal well project. This study shows that production is no longer proportional to the horizontal well length after a critical point. The critical point is calculated as a function of the length of the horizontal production section, flow rate, drawdown pressure, and other parameters. A step by step calculation procedure with examples is described with sets of graphical charts developed for illustrating the relationships between the various parameters. The results can be used directly to determine the optimum horizontal well length in multiple well projects.

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