Getting To Know Your Faults |
 | In the last decade, 3-D seismic techniques have completely revolutionised the structural and stratigraphic modelling of reservoirs and have led to a remarkable resurgence, world-wide, in the discovery of new fields. Some fields previously interpreted as lacking any significant structural control have for the first time been shown by 3-D surveys to contain important fault and fracture trends, such as the super-giant Ghawar Field of Saudi Arabia. However, most faulting within reservoirs occurs at a sub-seismic scale and the complexities of fault zones are often not considered. The details of these faults and fractures are best revealed by a combination of borehole images and cores.
This article discusses the occurrence of fault damage zones in which cataclastic fracturing has a profound influence upon reservoir properties. Examples are given of modern techniques of borehole imaging and core analysis to characterise the importance of such fracture systems. |
Read this article |
Go With The Flow (Part 1) |
 | Palaeotransport analysis is a valuable sedimentological tool in reservoir and basin characterisation. Such interpretations can be derived using borehole images. This document provides an introduction to palaeotransport analysis from borehole images and dipmeter data. It details the applications, methodology and pitfalls associated with such an analysis. This will enable the reader to help plan image tool campaigns, comprehend technical approaches and enable them to get the most from an interpretation report.
Intriguingly, there is very little meaningful literature on the effective use of dipmeter data or borehole images for palaeotransport analysis. This article provides a review of the techniques in borehole image palaeotransport analysis and some guidelines to the interpretation of the results. |
Read this article |
Finding Yourself in Deep Water (Part 1) |
 | Spectacular successes in deep water drilling have led to a new era in exploration within turbiditic systems around continental margins.
Identifying prize targets in deep water is a serious financial commitment, consequently a good understanding of turbiditic sedimentary systems means risk can be reduced. Borehole images play an important role in providing such information, but require experienced interpreters to recognise such details.
This article outlines the interpretation reliability of the tools involved, presents a summary of the key interpretation methodologies, and also considers some more advanced applications of data derived from deep water sedimentary systems using borehole image and dipmeter data.
|
Read this article |
Finding Yourself in Deep Water (Part 2) |
 | Part I of this article reviewed the types of borehole image tools and the styles of geological features which can be resolved in deepwater sediments. The general approach to interpretation was outlined and considered in the context of the major depositional environments which can be found in a deep marine setting.
Part II considers the types of directional data and thin bed information which can be resolved from images. The important geological contributions of LWD image logs in deepwater sediments are reviewed and emerging reservoir modelling applications are considered. |
Read this article |
SPWLA 2007: LWD azimuthal density logging in Liverpool Bay, UK as an aid to completion planning via fault and fracture detection |
 | A logging while drilling (LWD) Azimuthal
LithoDensity (ALD) imaging tool was run in horizontal
dual lateral wells 110/15-L13 and 110/15-L13z with the
aim of identifying fault and fracture intersections. The
wells are located in the BHPBilliton operated Lennox
Field, in the Liverpool Bay area of the East Irish Sea
Basin, United Kingdom Continental Shelf (UKCS).
Image quality is good and numerous geological features
have been identified. Fractures have been classified as
either high density or low density, relative to host
formation. A total of 184 fractures have been identified
in L13 while 121 fractures were identified in L13z.
When corrected for borehole bias, 529 fractures are
calculated to intersect L13 while 241 fractures are
calculated to intersect L13z. Fracture orientations are
consistent with the strike of regional scale faults.
Fractures in L13 and L13z strike north-south, with
minor north-northwest to south-southeast components.
Significant drilling mud losses in the vicinity of
fractures suggest that some fractures were open and
therefore acted as fluid escape conduits. Drilling mud
seepages within intervals that contain no apparent
fractures may be related to fracture cuts that are below
the resolution of the ALD sensor. It is also possible
that some fractures became dilated after passage of the
LWD tool assembly.
Real time utilization of the LWD and ALD data
enabled the operator to plan and locate External Casing
Packers (ECPs) and the completion string quickly and
accurately, thus removing conventional logging delays
(and costs) while the drilling rig was on location. |
Read this article |
