Mauddud Fractured Reservoir Analysis, Greater Burgan field: Integrated Fracture Characterization using Static and Dynamic Data
Authors: Alzankawi Omran , Al-Houti Reham , Ma Eddie , Ali Farida Ali , Alessandroni Mauro , Alvis Mariana 
Published: May 2016

The understanding of the flowing behavior coming from Mauddud carbonate reservoir in Greater Burgan field has always been a matter of debate. This reservoir is composed of tight complex carbonates with net gross pay that ranges from 10 up to 25 feet. Its porosity response is generally low, as well as its matrix permeability. The best strategy for reservoir exploitation it is for sure by mean of horizontal drilling but results did not match expectative, since some unsuccessful wells were drilled.

For aforementioned reasons it is crucial to understand and characterize the presence of fractures in the Mauddud carbonate reservoir as well as the presence of vugs and leached features in order to establish if the observed production is related to matrix or to the fracture network contribution. The understanding of the relationship between matrix characteristics, fracture distribution, and well production will allow planning a better developing strategy for the sweet spots.

This paper describes initially the results of geological fracture characterization, and then presents the integration of such results with available dynamic data. Main results obtained from geological characterization are that fractures are mainly fault-related, limited in height by the carbonate reservoir, and sometimes oil bearing even if no oil stains were found in matrix. The study of dynamic data, combined with the geological results, was mainly dedicated to recognize the well flowing regimes that cannot be associated only to matrix contribution, but that are probably due to a flowing from fractures. Obtained results could lead to better diagnostic and better development strategies in this challenging reservoir.

Introduction

The Greater Burgan Field lies to the South east of Kuwait; 35 km south of Kuwait City, near Ahmadi and cover a surface of about 1200 square kilometers. It consists of three giant fields: Burgan, Magwa and Ahmadi (Fig. 1). It is one of the world's largest sandstone oil field, with major reservoir units found in the Albian-Cenomanian sequences. The Mauddud formation is a pure carbonate inner ramp succession, deposited immediately above the maximum floding surface (MFS). Carbonate lithofacies comprise mostly limestone and dolomite, plus transitional lithologies such as dolomitic limestones or calcareous dolomites. Reservoir quality is considered poor with an average porosity of 18% and permeability ranging between 0.1%-10% mD in average. The object of the study was to conduct an integrated fracture characterization of the Mauddud formation using static data (Borehole Image logs-BHI, cores and wireline logs) geophysics, and dynamic data (production data, flowmeter, welltests) to determine the types of fractures and their occurance in order to predict their flowing behavior. This information was integrated in order to interpret if the current Mauddud production can be due to matrix contribution or due to the impact of fractures. Used methodology has been already described by (Fonta et al. 2005; Guaiquirian et al., 2007; Singha Ray et al., 2012). And based on this study, opportunities were evaluated once more to revive many non producing wells which showed sharp decline due to tight rock matrix. Wells were screened for stimulation by using various proven new technologies. Acid Frac, Stage Frac, near well bore SurgiFrac and Matrix Acid techniques have been applied with varying results. Advanced placement technique like distributed temperature profiling was used in some of the jobs, some of these actions and applied technologies will be addressed in the following pages.