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.

Unconventional resource plays have recently been traded favorably in Acquisitions and DivestituresЉA&DЉ markets due to view of having lower risk and or better growth prospects compared to conventional resources ЉDevashish, 2014Љ. For unconventional plays, the reservoir geological boundaries usually extend beyond the limits of the acreage holding. Some of the major uncertainties in the unconventional plays reserves and resources assessment tend to be: the basis of declaration of discovery, the definition of the project boundary (technically and commercially), the categorization of reserves/resources referenced to the degree of uncertainty, and the appropriate methods to estimate the production forecasts and ultimate recovery.In this paper we present field example from unconventional resource play. The reasons for variations between different reserve estimations for the same asset (based on real case history) are explained, with recommendations for practical considerations. These include using diagnostic techniques of production data to establish production forecasts that satisfy the reasonable certainty criteria required for booking reserves. We will discuss examples for the implementation of the reserves categorization in unconventional resource plays according to the guidelines of SEC and SPE Petroleum Resources Management System ЉSPE-PRMSЉ. Additionally, some practical rules for the assessment of contingent resources in unconventional plays will be discussed.It should be noted that reserves categorization in unconventional resource plays is an area that is subject to different interpretations across the industry, resulting in variations in the results of reserves estimation between different estimators. The contribution of this work is a critical discussion on these differences, and how they relate to the uncertainty on production forecasts. It is our expectation that better understanding of the uncertainty leads toward best practices for reserves estimations throughout the industry.