The Impact of Fault
-Zone Materials from Hydrocarbon Accumulation: From Outcrop Analogue from Southeastern Nigeria
Olugbenga A. Ehinola1 and Adeboye S. Adeyemi2
1Geology, University of Ibadan, Ibadan, Nigeria
2OTG-W Dept., Mobil Producing Nigeria Unlimited, Lagos, Nigeria
The contrasting capacity of faults to act as seal in some cases, and to serve as migration conduit in others, has been the subject of numerous researches, especially in the oil industry. However, a lot of previous work on the impact of these faults to hydrocarbon accumulation and production has mostly addressed fault
juxtaposition, rather than the properties of
fault
zone materials, as the sealing mechanism.
The aim of this study is to analyse the relative impact of fault
gouge materials and
fault
juxtaposition as sealing mechanism, and to develop a method to predict fluid transmissibility and / or containment by
fault
zone materials, using outcrop dataset obtained from southeastern Nigeria. In addition to field mapping and detailed description of
fault
zone and juxtaposed materials at the outcrop, integrated modeling of
fault
surface and elevation data and estimation of the permeability of the studied
fault
using GXII and Shale Gouge Ratio respectively were adopted. To minimize the limitation of the lack of good 3D seismic, pressure and production data, analogous data from other locations of similar geologic settings are incorporated.
The result shows that four different scenarios were possible in the study area and these include: sand-sand, sand-shale, shale-sand and shale-shale relationships across the faults. The attribute from each of these lithologic pairs was integrated with the properties of the fault
zone materials to develop a relative impact-matrix for ranking the different scenarios. It can be deduced that both the nature of materials juxtaposed across a
fault
and the character of materials in the
fault
zone play significant, and complementary roles in fluid control across a
fault
. This suggests that field study approach can be adopted in investigating the impact of
fault
zone materials.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery