Deciphering the Performance of Multi-Lateral and Extended Reach Wells for Reserves Evaluation in Unconventional Resource Plays

Recent advancements in well design and completion technology have been tested in unconventional resource plays with wide variety of results. This paper discusses the evolution and performance analysis of the different well designs in a tight unconventional oil play in North America. A brief description is given of the different chronological well types in the play (i.e. standard horizontal wells, multi-lateral wells, and extended reach horizontal wells). The performance of such advanced wells is analyzed. The flow regimes encountered around multi-lateral and extended reach horizontal wells are described using diagnostic plots of time rate and pressure (TRP) data. These regimes are related to Arps exponent b-factor. So far, there is little information of such flow regimes or the ranges of b-factor for multi-lateral wells in tight unconventional plays. In multi-lateral and extended reach horizontal wells, a period of frac water cleaning may be seen at the initial production. Apparent early bilinear or linear flow regimes might be observed afterwards. In this tight oil play, later multi-phase effects dominate the flow regimes and cause deviations from the early bilinear and linear flow. Late second linear flow regime is not seen in the analyzed data of standard horizontal wells, multi-lateral wells, or extended reach horizontal wells. In this play, multi-phase effects cause late time lower b-factor. In many instances, late time b-factor is lower than 1. This work emphasizes on the reserves estimation of these modern wells in this play. Extended reach horizontal wells have shown better late time b-factor and normalized Initial Production of 90 days "IP90" per lateral length compared to multi-lateral wells. This might give an indication of the higher completion efficiency in the extended reach horizontal wells. Based on this work, Extended reach horizontal wells have higher Estimated Ultimate Recovery "EUR" compared to both multi-lateral and standard horizontal wells. Development of unconventional plays by drilling longer single lateral horizontal wells while reducing the inter frac stages spacing is becoming the norm. This work helps to decipher the performance of multi-lateral and extended reach wells in unconventional plays. This leads to improving the development concepts and reserves evaluation methods of these modern wells in unconventional formations.