In terms of well productivity, unconventional resource plays are not created equally, and, to throw another wrench in the mix, not all of one particular play is created equally. This goes beyond the geographic 2D perspectives of the play, as the stratigraphic 3D sequence of a reservoir also has to be taken into account. The image below shows reported horizontal Bone Spring producing wellbores in a subsurface view to elaborate on this concept.
Using DI Transform GG&E interpretive software, one can view the variation in targeted depth between the top and the base of the Bone Springs formation. Why does this matter? Ideally, well planners and drillers want to land the lateral extension of a horizontal wellbore within a targeted zone that will provide the best production volumes. Subsequently, analysts and the like must perform evaluations on a best efforts, normalized basis to obtain the most accurate and relevant results. In performing this data analysis, the reported reservoirs of production supplied to the state’s oil and gas regulatory agency are adequate for only a broad-scale comparison.
For example, when querying horizontal Bone Spring wells in the Delaware Basin, a few of the most common reported reservoir naming conventions are some iteration of the spelling of Bone Spring, Trend Area and Wolfbone Trend (yes even for horizontals). This may very well be sufficient for some analytical workflows; however, it is not a true apples to apples comparison. This is where DI Geology Play Assessments can assist in order to get a granular, detailed perspective of a reservoir.
The Delaware Basin Play Assessment
The Delaware Basin Play Assessment divides the Avalon/Bone Spring formations into eight interpreted zones. For the scope of this post, I have limited the zones down to four: the Avalon and the First, Second, and Third Bone Spring intervals. Lithological properties vary within each respective zone and can therefore offer differing approaches to completion design and ultimately oil and gas production volumes. The cross section below showing gamma ray and deep resistivity logs indicates the varying stratigraphic sequences picked on changing geologic events in the Leonardian-aged section.
The entire Avalon/Bone Springs has a thickness that ranges from roughly 2,000 to 4,000 feet, depending on the portion of the basin under observation. The isopach map below gives a spatial representation of the gross thickness of the entire Avalon/Bone Springs section throughout the Delaware Basin. This may even shed a bit more light on the range in possibilities of where a lateral wellbore can be strategically placed.
So you may be wondering how these horizontals perform based on where they are penetrating the reservoir. I have mapped out each major surface within the Avalon/Bone Springs and spatially/stratigraphically joined the well locations and their perforation intervals to the interpreted sections on a true vertical depth scale. (This is not a definitive statement on which interval is the best. Many other geologic and engineering factors come into play when analyzing a well’s productive potential. This is simply an observation in how well performance is trending when defined by each interpreted section.)
I have chosen peak month rate as the metric of comparison since it provides the largest data set of wells and since there is generally a decent correlation between peak month and short-term cumulative rates. After sub-setting down to horizontal Avalon/Bone Spring wells within the geographic study area, with readily available digitized directional surveys, production, and perforation intervals we have a total of 428 wells to compare.
I hope that you have found this article interesting. If you have any questions on the DI Geology Delaware Basin Play Assessments feel free to contact your Drillinginfo sales representative or your go-to support specialist.
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