Jadi, Menayer Al (Kuwait Oil Company, Kuwait) | Kumar, Pranay (IFP Middle East Consulting, Bahrain) | Lislaud, Frederic (Beicip Franlab, France) | Robert, Joël (Beicip Franlab, France) | Alessandroni, Mauro (Beicip Franlab, France) | Lefebvre, Christian (IFP Middle East Consulting, Bahrain) | Groen, Vincent de (Beicip Franlab, France) | Vigier, Louise (Beicip Franlab, France) | Datta, Kalyanbrata (Kuwait Oil Company, Kuwait) | Hafez, Karam (Kuwait Oil Company, Kuwait) | Taneja, Hans (Kuwait Oil Company, Kuwait) | Bhattacharya, Muktibrata (Kuwait Oil Company, Kuwait) | Bond, Deryck (Kuwait Oil Company, Kuwait)
An integrated reservoir study of the Magwa Marrat reservoir has been completed recently. This study was carried out to support the continued development of the reservoir, in particular the planning of a secondary water flood.
The initial part of the study concentrated on reservoir characterization and reservoir performance over a long period, in the order of 30 years, of primary recovery, followed by analysis of a recent pilot water flood. A better understanding of the controls of flow and the role of fracture corridors and diffuse fractures was achieved through and integration of geophysical, petrophysical and dynamic data including tracer tools and in particular through a dynamic model of the water flood pilot. The uncertainties related to structural extension, especially on the flanks of the field and related to aquifer support, were also recognized.
Later on static and dynamic models were built, first around the pilot water flood area and then for the entire reservoir. These models have been used for development planning.
This paper gives an overview of the integrated study but concentrates on the features, detailed below, that were key to better understanding the fluid flow physics and to achieve a satisfactory "history match".
A single porosity model that accounted for matrix permeability, local enhancement to permeability within restricted fracture corridors and the effect of diffuse fractures in "tight" zones was adopted. Matrix permeability values were based on the results of a rock typing study. Static and dynamic pressure, oil production and water movement matching was achieved by making limited and realistic changes to fracture zone permeability, fracture zone extent and some fine tuning of matrix permeability. Well productivities, pressure transient tests, interference tests and production log data were used to guide and validate the history match.
Water-cut match was further improved by making reasonable changes to the structural model in regions where significant structural uncertainty was recognized.
Gomez, Ernest (Schlumberger) | Al-Faresi, Fahad A. Rahman (Kuwait Oil Company) | Belobraydic, Matthew Louis (Schlumberger) | Yaser, Muhammad (Schlumberger) | Gurpinar, Omer M. (Schlumberger) | Wang, James Tak Ming (Schlumberger) | Husain, Riyasat (Kuwait Oil Company) | Clark, William (Schlumberger) | Al-Sahlan, Ghaida Abdullah (Kuwait Oil Company) | Datta, Kalyanbrata (KOC) | Mudavakkat, Anandan (KOC) | Bond, Deryck John (Kuwait Oil Company) | Crittenden, Stephen J. (KOC) | Iwere, Fabian Oritsebemigho (Schlumberger) | Hayat, Laila (KOC) | Prakash, Anand (KOC)
The Burgan Minagish reservoir in the Greater Burgan Field is one of several reservoirs producing from the Minagish formation in Kuwait and the Divided Zone. The reservoir has been produced intermittently since the 1960s under natural depletion. A powered water-flood is currently being planned. The pressure performance of the reservoir has proved hard to explain without invoking communication with other reservoirs. Such communication could be either with other reservoirs through the regional aquifer of through faults to other reservoirs in the Greater Burgan field. Recent pressures are close to the bubble point.
A coarse simulation model of the nearby fields and the regional aquifer was constructed based on data from the fields and regional geological understanding. This model could be history matched to allow all regional pressure data to be broadly matched, a result which supports the view that communication is through the regional aquifer. Using this model to predict future pressure performance suggested that injecting at rates that exceeded voidage replacement by about 50 Mbd could keep reservoir pressure above bubble point. It was recognized that the process of history matching performance was non-unique. This is a particular concern in the context of this study because the model inputs that were varied in the history matching process included aquifer data that was very poorly constrained. To address this problem multiple history matched models were created using an assisted history matching tool. Using prediction results from the range of models has increased our confidence that a modest degree of over-injection can help maintain reservoir pressure.
This paper demonstrates the utility of computer assisted history match tools in allowing an assessment of uncertainty in a case where non-uniqueness was a particular problem. It also emphasizes the importance of understanding aquifer communication when relatively closely spaced fields are being developed.
Turkey, Laila (KOC) | Hafez, Karam Mohamed (KOC) | Vigier, Louise (Beicip) | Chimmalgi, Vishvanath Shivappa (Kuwait Oil Company) | Dashti, Hameeda Hussain (Kuwait Oil Company) | Datta, Kalyanbrata (KOC) | Knight, Roger (KOC) | Lefebvre, Christian (Beicip-Franlab) | Bond, Deryck John (Kuwait Oil Company) | Al-qattan, Abrar (KOC) | Al-Jadi, Manayer (Kuwait Oil Company) | De Medeiros, Maitre (Beicip) | Al-Kandari, Ibrahim (Kuwait Oil Company)
A pilot water flood was carried out in the Marrat reservoir in the Magwa Field. The main aim of this pilot was to allow an assessment of the ability to sustain injection, better understand reservoir characteristics. A sector model was built to help with this task.
An evaluation of the injectivity in Magwa Marrat reservoir was performed with particular attention to studying how injectivity varied as injected water quality was changed. This was done using modified Hall Plots, injection logs, flow logs and time lapse temperature logs.
Data acquisition during the course of the pilot was used to better understand reservoir heterogeneity. This included the acquisition of pressure transient and interference data, multiple production and injection logs, temperature logging, monitoring production water chemistry, the use of tracers and a re-evaluation of the log and core data to better understand to role of fractures.
A geological model using detailed reservoir characterization and a 3D discrete fracture network model was constructed. Fracture corridors were derived from fractured lineaments interpreted from different seismic attribute maps:
A sector model of the pilot flood area was then derived and used to integrate the results of the surveillance data. The main output is to develop an understanding of the natural fracture system occurring in the different units of the Marrat reservoir and to characterize their organization and distribution. The lessons learned from this sector modeling work will then be integrated in the Marrat full field study.
The work described here shows how pilot water flood results can be used to reduce risk related to both injectivity and to reservoir heterogeneity in the secondary development of a major reservoir.