Second Bone Spring Borehole Image Derived Depositional Facies Characterization: Case Study From the Delaware Basin, West Texas

Abstract

The Bone Spring Formation is a Permian deposit characterized by a variety of facies, from well layered fine grained basinal turbiditic deposits to coarser grained flow deposits, to slumps and complex mass transport deposits. This case study focus on integration of conventional core analysis and routine and advanced wireline logs including nine borehole image logs, all acquired within a 20 miles radius from the core.

Core analysis included lithofacies, identification of sedimentary and/or biologically and/or chemically induced structures.

The borehole image logs were analyzed for fracture distribution, identification of sedimentary facies, and their variation in the vertical and lateral space.

A lithofacies catalog (mudstone, carbonate-rich mudstone, thick bedded silt, and thick bedded carbonate-rich silt) was produced and applied to all the nine wells by comparison between core, borehole images and advanced spectroscopy log available in one well.

From the analysis of the borehole images the structure is consistently gently dipping to the WNW with a rotation to the SE in the Southern most well. This is justified by the presence of a major fault, dissecting the basin into two parts. This major fault is also coincident with a rotation of the insitu max stress from E-W to WNW-ESE. Natural fractures show a strike bi-modal distribution: NE-SW and WNW-ESE. The southernmost well shows a different result with a NW-SE predominant and a NE-SW secondary trend. The presence of interpreted open fractures increases towards the West of the study area.

Facies analysis on the borehole image highlighted the presence of laminations, dewatering structures, mud clasts, intense bioturbation, large concretions, oblate concretions, pyrite, patchy cement, cross laminations and highly deformed facies.

Newly applied technologies allowed the quantification of laminations from high-resolution image data. Laminations frequency and thickness can give indications on sedimentary energy and provides information on the depositional settings.The variation on lamination thicknesses and densities supported in the identification of facies.

The different depositional environments interpreted from this dataset are: deep basin, distal turbidite lobe, and distributary channels.

The integration between core and image logs helped propagate the facies and depositional environment interpretation from expensive cored wells to much more cost-effective logs datasets and it helped also in reducing wellbore risk.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018