Print this pageAAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Integrated Dolomite Characterization of Deep Jurassic Formation, Middle Marrat, Minagish Field, Kuwait: A Case Study
(1) WK, Kuwait Oil Company, Ahmadi, Kuwait.
(2) Schlumberger, Kuwait, Kuwait.
The Minagish Marrat is a deep, over-pressured, tight carbonate reservoir with light Jurassic oil production history of 24 years. As many as 16 deep wells penetrate this reservoir of which 12 were completed as naturally flowing producers. Petrophysical characterizations of this complex carbonate reservoir is a challenging task due to constraints imposed by large well spacing, small well bore diameter, use of oil based mud, HP-HT coupled with H2S environment. Reservoir characterization away from wellbore is equally challenging due to inadequate resolution of 3D seismic data at depths exceeding 11,000 feet. Understanding the role of both primary depositional and secondary digenetic processes in porosity development through integrated reservoir characterization assumes great significance in such circumstances.
This paper documents efforts to define accurate mineral model for probabilistic petrophysical analysis specially dolomite characterization, which plays important role in reservoir development being less susceptible to porosity reduction under high overburden pressures and deep settings. As evident from core analysis results (porosity and permeability), dolomitization plays a significant role in increasing the storage capacity. So quantification of dolomite is highly necessary to not only to understand reservoir rock quality but also as a key input into the static and dynamic reservoir modeling. However, the same is difficult in the absence of special logs like neutron capture spectroscopy data which provides a better solution. Conventional open hole logs (density, neutron and sonic) have their own limitations and uncertainty involved due to several factors such as: barite mud effect, oil base mud invasion, complex lithology, sensitivity etc. and hence alone cannot be used with full confidence for a complete characterization. Notwithstanding this limitation, at this end, an attempt was made to solve this dolomite volume and build a good mineralogical model through an integrated workflow approach where information from high resolution sequence stratigraphy, core and electrolog based rock typing, core analysis and the available conventional logs were used. This integrated approach was followed for few key wells with all inputs to build the probabilistic multi-mineral model, with reasonable confidence and define the parameters which were later applied effectively for all other wells in the field for successful dolomite mapping and identification of the zones of interest. The results were further incorporated in the static reservoir modeling providing a new dimension to the reservoir characterization (reported elsewhere). This approach is planned to be validated and calibrated with neutron capture spectroscopy data in the future wells.