Rahaman, Mafizar (Kuwait Oil Company) | Hafez, Mohamed (Kuwait Oil Company) | Ibrahem, Al-Saleh Lulwa (Kuwait Oil Company) | Mudavakkat, Anandan (Kuwait Oil Company) | Rajagopal, Rajesh (Kuwait Oil Company)
This paper presents the use of prestack geostatistical inversion (PGI) technique, for the delineation of thin sand intervals in the Wara Formations in the Magwa and Ahmadi fields, Kuwait. In this area, Wara Formations is predominantly sand and shale sequences, with higher proportion of shaliness compared to the adjacent Burgan field. Wara sands are good producers of hydrocarbon in the study area. The low P-impedance contrast between the sand and shale makes P-Impedance ineffective to discriminate them. The Vp/Vs ratio from the PGI is found to effectively discriminate these sand units from shale.
The main inputs for PGI study are well log data, well log statistics and seismic angle stack data. Petrophysical analysis was carried out, which is essential for identifying reservoir facies. Two lithologies in Wara Formation are defined using well log analysis with Vshale cut off. Detailed well log statistics analysis (vertical size, layer constraints and lithology proportions) was carried out, which is also a primary input for the PGI study. Seismic angle stacks were aligned and amplitude-balancing were also carried out. After obtaining optimized inversion parameters, PGI was run. It provided the multiple plausible realizations of P-impedance, S-impedance, Vp/Vs and lithology volumes, which are further used and co-simulated to generate porosity volumes. Porosity and most probable lithology volumes were generated for mapping the reservoir distribution in the area. Two blind test results provided good match and further determined the reliability of the PGI. The study shows additional porosity development towards north eastern part of Magwa and Ahmadi fields.
Presentation Date: Tuesday, October 16, 2018
Start Time: 9:20:00 AM
Location: Poster Station 7
Presentation Type: Poster
Chen, Taiwen (Kuwait Oil Company) | Jaseem, Mohamed Hafez (Kuwait Oil Company) | Mudavakkat, Anandan (Kuwait Oil Company) | Hafez Abd Rabu, Karam Mohamed (Kuwait Oil Company) | Madhavan, Sethu (Kuwait Oil Company)
This paper presents a case study for lithology prediction of the Wara and Burgan Formations in Kuwait, using the prestack geostatistical inversion technique. The main objective of this study was to discriminate sand from shale, and to identify thin sand layers within Wara and Burgan Formations. Petrophysical editing was carried out to condition logs, as reliable logs are required for lithology classification and inversion. Two lithologies (sand and shale) were identified on well logs using Vsh (volume of shale) as cutoffs for Wara and Burgan Formations. Detailed well log statistics analysis (vertical size, statistical layer constrains, lithologies and their proportions) was carried out, and these statistical parameters were direct inputs for the geostatistical inversion. Seismic angle stacks were amplitude-balanced and aligned properly. Several inversion QC procedures were incorporated in the workflow to determine inversion parameters, and to optimize the quality of inversion results. After optimal inversion parameters were obtained, prestack geostatistical inversion was carried out to generate elastic properties (P-impedance, S-impedance, and Vp/Vs) and discrete property (lithology) with the integration of well and seismic data. Furthermore, porosity and sand frequency properties were generated, and they were used for mapping the sand distribution in the study area.
Presentation Date: Tuesday, September 26, 2017
Start Time: 1:50 PM
Presentation Type: ORAL
Mudavakkat, Anandan (Kuwait Oil Company) | Mukherjee, Pradip Kumar (Kuwait Oil Company) | Al-Ghareeb, Aisha Yousef (Kuwait Oil Company) | Rabu, Karam Mohamed Hafez (Kuwait Oil Company) | Kumar, Rajive (Kuwait Oil Company) | Edwards, Keith (Kuwait Oil Company) | Aziez, Yasmine (CGG) | Pandolfi, Daniela (CGG) | Coléou, Thierry (CGG)
This 4D feasibility study for Wara-Burgan Cretaceous reservoir in Greater Burgan Field, Kuwait is attempted aiming to model the 4D effects, as water-flood aided production progresses over the future years. In the first phase of the study, a Petro Elastic Model (PEM) is calibrated to well data and changes of elastic parameters are computed for different scenarios of fluid saturation and reservoir pressure at well locations (1D data). In the second phase, 4D effects are computed at the whole reservoir interval using static and dynamic reservoir properties from flow simulation model. Spatial distribution of 4D effects and the effect of added noise and their relationship with respect to temporal variations of elastic properties are analyzed to fully understand their characteristics and investigate which monitoring network (Conventional or Permanent) can better record the features of 4D effect.
Phase-I: Petro-elastic Modeling (PEM) definition and 1D data analysis
The first phase of the project is to define and calibrate the PEM which better describe the Wara-Burgan reservoir: an heterogeneous reservoir deposited in fluvio- deltaic and tidal condition, where thin stacked channels with sand are intercalations of shale and sand continuity is highly unpredictable. But middle and lower Burgan are thicker sand bodies and fluvial dominated. The variability inherent to the depositional style leads to a complex reservoir scheme.
In-situ logs (using Wara and Burgan formations at once) from 6 wells are used to perform cross-plot analysis and give a first indication regarding lithology’s discrimination using elastic properties (Ip, Vp/Vs). 4 wells show similar behaviour in term of lithology (Sand/Shale) discrimination.
The PEM which allows to include effective porosity (Fraction), water saturation (Fraction), oil saturation (Fraction), lithostatic and pore pressure (MPa), volume of clay (Fraction) and fluid reservoir properties, (gravities, pressure and temperatures), in order to predict elastic properties is the stiff sandstone model based on Hertz- Mindlin’s model.
Al-Zuabi, Abdullah (Kuwait Oil Company) | Bahman, Hussain (Kuwait Oil Company) | Al Zankawi, Omran (Kuwait Oil Company) | Kotecha, Rohit (Kuwait Oil Company) | Mereno, Beltran (KOC) | Mukherjee, Pradeep (KOC) | Mudavakkat, Anandan (KOC) | Al-Sabea, Salem (Kuwait Oil Company) | Al-Hamoud, Jamal (Kuwait Oil Company)
With increasing complexity to tap oil in clastic reservoirs due to stratigraphy, structure and facies variation optimization of placement of horizontal well has become a key to success. To augment this aspect Kuwait Oil Company (KOC) has established Geosteering Centre which has become the hub for decision making while the well is getting drilled for landing at top of reservoir or lateral is being drilled.
The Great Burgan field located in South East Kuwait asset of KOC major Horizontal drilling campaign started in 2005 mostly in clastic reservoirs.. This field been on the production since 70 years, most of its development wells were drilled and completed as vertical or deviated. It was decided to utilize horizontal well technology to drill thin productive layers. This paper illustrates an integrated approach using 3D-Model along with seismic analysis, knowledge sharing and most advanced Geosteering technology to successfully transfer, edit, and interpret the dynamic data in real time to monitor the drilling progress specially the lateral section. This state-of-the-art computing and visualization technology enables geologists to take corrective measures keeping the well in sweet zone as much as possible, through direct satellite communication with the rig's Geosteering unit and planned well course VS actual trajectory was continually updated and well path corrected based on information received.
The Geosteer center moved Field Development South-East Kuwait to a whole new level of collaboration that is equipped with latest in visualization, communication and computer technology in order to properly place and geologically navigate one of the world's largest siliciclastic reservoirs.
Today the interactive process of geosteering, using real-time data and making real-time decision has resulted in mitigating inherent geological risk in order to optimize the best drilling results for each horizontal well and to ensure an effective implementation of all new ongoing field development plans and made it possible to tackle thin reservoirs which now can be drilled economically.
Kuwait oil Company initiated horizontal drilling approach since early 1990's, and to place the wells successfully in the desired reservoir, an integrated approach using static model and subsurface analysis, knowledge sharing, effective communications and state of the art geosteering technology have all been utilized in order to have a successful well placement.
Bardalaye, Jayanta (Kuwait Oil Company) | Al-Azmi, Khalid Huomood (Kuwait Oil Company) | AL-Azmi, Mohammed Saad (Kuwait Oil Company) | Belal, Dawood Salman (Kuwait Oil Company) | Mudavakkat, Anandan (Kuwait Oil Company) | Mukherjee, Pradip Kumar (Kuwait Oil Company) | Al-Sabea, Salem Hamad (Kuwait Oil Company)
The Greater Burgan Field is the oldest producing oil field of Kuwait. Till date, more than 1200 wells have been drilled in the field. Construction of surface production facilities, power line corridors, roads as well as office and housing complexes for its employees have put severe constraints on surface locations for drilling new wells. A fault block in the Ahmadi ridge that was expected to be geologically very prospective for hydrocarbon accumulation could not be accessed for a long time as it was below the Kuwait Oil Company's office complexes. Structural complexity and poor quality of seismic data around that area also added to the uncertainty.
To reach the producing Wara and Burgan sands, the wells have to be drilled through the carbonate Dammam, Radhuma and Tayarat formations which are potential loss zones - more often than not leading to total mud loss. Deviated wells drilled so far in the field were, therefore, restricted to a maximum inclination of 45 degrees with the kick-off point located as deep as possible to minimize losses. This put a severe constraint on the horizontal drift achieved at pay zone level.
Two high-angle deviated wells were successfully planned and drilled with inclinations of 50 degrees or more with shallow kick-off depths to achieve a horizontal drift of upto 1 km to reach the hydrocarbons locked up below the company office complexes. The higher inclinations also helped in maximizing the reservoir contact and net pay of more than 100 ft was encountered in both the wells.
Kumar, Rajive (Kuwait Oil Company) | Hafez, Karam M. (Kuwait Oil Company) | Mudavakkat, Anandan (Kuwait Oil Company) | Al-Ghareeb, Aisha Y. (Kuwait Oil Company) | Hussain, Thekriat (Kuwait Oil Company) | Sharma, Ritesh K. (Arcis Seismic Solutions, TGS) | Chopra, Satinder (Arcis Seismic Solutions, TGS)
The Lower Zubair sand reservoirs have produced or shown oil in several but not all of the wells drilled in western and southeastern Kuwait. Evidence from the available core and log data analysis suggests that the Lower Zubair sand distribution consists of NE-SW trending estuarine channel fill. Thin due to their strati-structural nature, these Zubair sands are present at some places and absent at others. The tectonic activity in the area has resulted in faults and fractures in the interval comprising not only the Lower Zubair sands but the Middle and Upper Zubair sands as well. In general, the impedance contrast between these thin Zubair sands and the underlying Ratawi shale is poor. Therefore, the challenge is to identify not only the spatial variability of these Lower Zubair sands but also crosscutting faults and fractures. We address these challenges by first enhancing the bandwidth of the available seismic data using spectral inversion to estimate thin bed reflectivity, followed by relative acoustic impedance to map the reservoir heterogeneity, and that in turn followed by coherence and curvature attributes to detect minor faults and fractures.
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.