In multi-fractured horizontal wells, the wellbore is segmented into stages that are stimulated separately. This segmentation is traditionally geometrically based on a specific stage length (“geometric staging”); which is usually determined by trial and error including cost and production history considerations. However, this approach does not take geological and geomechanical properties into account. An alternative method for staging (“engineered staging”) uses these properties to determine the wellbore segmentation by grouping intervals with similar rock properties together; theoretically promoting a higher percentage of stimulated clusters and subsequently better production. This alternative method is not commonly used as data acquisition can be costly for a large group of wells.
In Pennsylvania, two pairs of wells were completed in order to understand the added value of engineered staging design. In one of them, a comprehensive suite of openhole logs was run in the horizontal leg of a dry gas well. The staging was then designed according to the measured rock properties and the well was stimulated using slickwater with plug and perf. Finally, a production log was run in the well after a year in order to determine the downhole contribution of each stage and cluster. After 400 days of production, the well cumulative production outperforms its offset with geometric staging by around 5 to 7%, potentially attributable to the engineered design but still within the expected statistical regional deviation between wells. Long term impact is yet to be determined.
In the other pair, no openhole log other than MWD Gamma-ray was run. However properties were projected from a nearby vertical pilot hole with logs onto the horizontal section of a well which was then completed using the engineered staging method. Here again production figures after a year are showing a potential benefit; but this time without the cost of data acquisition in the lateral.
This paper describes the process that was applied to achieve the engineered staging of these wells. It details the initial geological and geomechanical data acquisition or projection; then describes the design of the hydraulic fracturing engineered staging and finally discusses the performance of the wells.