--> The Challenge of Porosity and Facies Variability Along Lateral Wells: A Case Study From The San Andres Formation, Permian Basin

AAPG ACE 2018

Datapages, Inc.Print this page

The Challenge of Porosity and Facies Variability Along Lateral Wells: A Case Study From The San Andres Formation, Permian Basin

Abstract

Enhancing reservoir understanding in the Permian Basin is of paramount importance in the attempt of maximizing hydrocarbon recoveries from existing reserves. The utilization of advanced technologies in data acquisition and integration between different information boosts such knowledge.

Since 1991, the acquisition of borehole images has become an integral part in reservoir characterization logging campaigns. Structural features including dips, faults and fractures can be clearly identified. However borehole images can also be used to characterize Porosity distribution and facies variation.

The objective of this case study is to highlight lateral facies variability in carbonate reservoirs where fractures do not play a major role in production. Most porosity development in carbonate reservoirs can be attributed in part or in total to diagenesis. This is especially true in Permian reservoirs of the Permian Basin, nearly all of which are dolomitized.

The San Andres Formation, a major oil-producing reservoir in Texas and New Mexico, is a progradational stratigraphic unit consisting predominantly of carbonate facies. Lithofacies include Dolomite, Anhydrite, Limestone and Salt.

Deposition was cyclic; a cycle began with a transgression followed by a gradual shoaling-upward sequence and terminated with subaerial exposure.

In this study we tried to describe and interpret the lateral facies variation of the San Andres using borehole images and acoustic data that were acquired in 2 horizontal wells in the Central Basin Platform. Dips were used to identify the structure and a fracture analysis was performed together with an advanced porosity analysis. This was achieved by using an advanced technique called PoroTex that maps heterogeneities encountered in Carbonates. Statistical methods were used to divide the total porosity into fractions of Micro and Macro-porosity. The new approach of heterogeneity delineation is used to outline and classify macro-porosities in the form of vugs, fractures, solution enhanced bedding etc. A correlation between lateral facies variation and fracture distribution has been then established. A clear relationship between fracture intensity and proximity to Evaporites was also observed.

The San Andres wells have always been a challenge. However this study provide insights on how integrating geological analysis based on advanced acquisition and interpretation technologies with various other domains can be the key to identify production drivers.