Bigoni, Francesco (Eni S.p.A) | Pirrone, Marco (Eni S.p.A) | Trombin, Gianluca (Eni S.p.A) | Vinci, Fabio Francesco (Eni S.p.A) | Raimondi Cominesi, Nicola (ZFOD) | Guglielmelli, Andrea (ZFOD) | Ali Hassan, Al Attwi Maher (ZFOD) | Ibrahim Uatouf, Kubbah Salma (ZFOD) | Bazzana, Michele (Eni Iraq BV) | Viviani, Enea (Eni Iraq BV)
The Mishrif Formation is one of the important carbonate reservoirs in middle, southern Iraq and throughout the Middle East. In southern Iraq, the formation provides the reservoir in oilfields such as Rumaila/West Qurna, Tuba and Zubair. The top of the Mishrif Formation is marked by a regional unconformity: a long period of emersion in Turonian (ab. 4.4 My) regionally occurred boosted by a warm humid climate, associated to heavy rainfall. In Zubair Field, within the Upper interval of Mishrif Formation, there are numerous evidences of karst features responsible of important permeability enhancements in low porosity intervals that are critical for production optimization and reservoir management purposes.
In the first phase, the integration of Multi-rate Production logging and Well Test analysis was very useful to evaluate the permeability values and to highlight the enhanced permeability (largely higher than expected Matrix permeability) intervals related to karst features; Image log analysis, on the same wells, allowed to find out a relationship between karst features and vug densities, making possible to extend the karst features identification also in wells lacking of well test and Production logging information. This approach has allowed to obtain a Karst/No Karst Supervised dataset for about 60 wells.
In the second phase different seismic and geological attributes have been considered in order to investigate possible correlations with karst features. In fact there are some parameters that show somehow a correlation with Karst and/or NoKarst wells: the Spectral Decomposition (specially 10 and 40 Hz volumes), the detection of sink-holes at top Mishrif on the Continuity Cube and its related distance, the sub-seismic Lineaments (obtained from Curvature analysis and subordinately from Continuity), distance from Top Mishrif. In the light of these results, the most meaningful parameters have been used as input data for a Neural Net Process ("Supervised Neural Network") utilizing the Supervised dataset both as a Trained dataset (70%) and as a Verification dataset (30%). A probability 3D Volume of Karst features was finally obtained; the comparison with verification dataset points out an error range around 0.2 that is to say that the rate of success of the probability Volume is about 80%.
The final outcomes of the workflow are karst probability maps that are extremely useful to guide new wells location and trajectory. Actually, two proof of concept case histories have demonstrated the reliability of this approach. The newly drilled wells, with optimized paths according to these prediction-maps, have intercepted the desired karst intervals as per the subsequent image log interpretation, which results have been very valuable in the proper perforation strategy including low porous intervals but characterized by high vuggy density (Karst features). Based on these promising results the ongoing drilling campaign has been optimized accordingly.
Identification of tidal channels fairways is key for predicting behavior of areas at higher risk to water breakthrough or otherwise have a significant impact on the development and monitoring of reservoir performance. However, tidal channels in carbonates are not often easily characterized using conventional seismic attributes. It is important to decipher the complexity of the carbonate tidal channel architecture with integrated multisource data and a variety of approaches.
In this paper, petrological characteristics and petrographic analysis is conducted on well logs and validated carefully using core data. Then, the second step is to compare the carbonate channel systems with modern analogue in Bahama tidal flat and outcrop scales in Wadi Mi'Aidin (Northern Oman). Thereafter, the supervised probabilistic neural network (PNN) and linear regression method were undertaken to detect an additional channel distribution.
The relationship of high porosity with low acoustic impedance appeared mostly in the channel facies which reflects good reservoir quality grainstone channels. Outside these channels, the rock is heavily mud filled by peritidal carbonates and characterized by a high acoustic impedance anomaly with low quality of porosity distribution. The new observation of PNN porosity volume revealed a lateral distribution of the Mishrif carbonate tidal channels in terms of paleocurrent direction and the connectivity. Additionally, the prior information from core data and the geological knowledge indicate a good consistency with classified lithology. These observations implied that Mishrif channels consist of a wide range of lithology and porotype fluctuations due to the impact of depositional environment.
The work enables us to provide a new insight into the distribution of channel bodies, and petrophysical properties with quantification of their influence on dynamic reservoir behavior of the main producing reservoir. This work will not only provide an important guidance to the development and production of this case study, however also deliver an integrated work path for the similar geological and sedimentary environment in the nearby oil fields of Southern Iraq.
The objective of this work is to characterize the fault system and its impact on Mishrif reservoir capacity in the West Quran oil field. Determination and modelling of these faults are crucial to evaluate and understanding fluid flow of both oil and water injection in terms of distribution and the movement. In addition to define the structure away from the well control and understanding the evolution of West Qurna arch over geologic time.
In order to achieve the aim of the work and the structural analysis, a step wise approach was undertaken. Primarily, intensive seismic interpretation and building of structure maps were carried out across the high resolution of 3D-seismic survey with focusing on the main producing Mishrif reservoir of the field. Also, seismic attributes volumes provided a good information about the distribution and geometry of faults in Mishrif reservoir. The next step, it constructs 3-D fault model which will be later merged into the developed 3D geological model. West Qurna/1 oil field situated within the Zubair Subzone, and it is structurally a part of large anticline towards the north. The observation of seismically derived faults near Mishrif reservoir indicated en-echelon faults which refer to strike-slip tectonics along with extensional faults. The statistic of Mishrif interval faulting indicates a big number faults striking north-south along western wedge of anticline. The seismic interpretation, in combination with seismic attributes volumes, deliver a valuable structural framework which in turns used to build a better geological model.
In this paper, the work demonstrates a better understanding for the perspectives on the seismic characterization of the structural framework in the Mishrif reservoir, and also for similar heterogeneous carbonate reservoirs. Further, this work will ultimately lead to improve reservoir management practises in terms of production performance and water flooding plan.
Al-Hameedi, Abo Taleb T. (Missouri University of Science and Technology) | Alkinani, Husam H. (Missouri University of Science and Technology) | Dunn-Norman, Shari (Missouri University of Science and Technology) | Flori, Ralph E. (Missouri University of Science and Technology) | Alsaba, Mortadha T. (Australian College of Kuwait) | Amer, Ahmed S. (Newpark Technology Center/ Newpark Drilling Fluids) | Al-Bazzaz, Waleed H. (Kuwait Institute for Scientific Research)
The rate of penetration (ROP) plays a major role in reducing drilling costs, making it an important area of investigation. There are various controllable and uncontrollable factors that affect the ROP, and the variation in these variables affecting the ROP made it a very pivotal drilling parameter that has a significant effect on non-productive time. In this work, sensitivity and statistical analysis were carried out using data from over 1000 wells in Basra oil fields, Iraq. The scope of this work is to determine the effect of rheological properties on ROP, to provide a method for estimating the recommended range for drilling fluid properties based on data mining techniques.
In this work, huge real field data from over 1000 wells drilled in Basra oil fields, Iraq were gathered and analyzed to better understand the characteristics of a drilling fluid that enhance ROP and quantify the impact of each drilling fluid rheological properties on ROP. The data used in this study were collected from mud logging data, daily drilling reports (DDR), and geological information. Statistical and sensitivity analyses were performed in order to identify the relationship between ROP and drilling fluid rheological properties. The correlation coefficient (CC) was utilized to understand the effect of solid content (SC), yield point (Yp), and plastic viscosity (PV) on ROP. The results showed that SC is the most influential rheological property on ROP, then PV and finally Yp. In addition, this work demonstrates how bit hydraulics can be improved by means of modifying the rheological properties rather than adjusting the flow rate or nozzle size.
Large-scale collection and interpretation of field data or in other words "data mining" can be considered as a strong tool in understanding the impact of different parameters on the ROP in order to estimate the recommended range of rheological properties, which will result in improving the ROP.
The objective of this work is to characterize the porosity distribution and the types of carbonate facies in the Mishrif Formation in the West Qurna/1 Oil Field using seismic inversion results, well log data and rock physics modeling. Identification of the pore system and the spatial distribution of lithofacies are keys for constructing Mishrif reservoir model, which have a great impact on the development of the most prolific reservoir in the field (Mishrif zone).
Seismic inversion involves the interpretation of elastic properties for facies based on the seismic response. It enables the modelling of lithology and porosity distribution in 3D space away from well control. In order to achieve the aim of the work, a step wise approach will be taken. First of all, deterministic seismic inversion was applied across the high resolution of 3D-seismic survey data over the West Qurna/1 Field. Then, the vertical distribution of porosity and facies recognition based on well log data and its relationship with elastic properties, integrated with seismic inversion results for validating at Mishrif intervals.
Deterministic seismic inversion was undertaken on the post-stack seismic dataset. The interpretation of seismically derived characterization in Mishrif reservoir indicated a different lateral distribution of acoustic impedance and three regions of channel (north, southwest and east). It can be seen a high acoustic impedance anomaly outside the channel in the western field sector which is heavily mud supported by peritidal carbonates (low quality facies of the reservoir). Whereas, carbonate tidal channel displayed a low acoustic impedance which reflect high porosity and good reservoir quality (grainstone channel or sholas). Furthermore, the interpretation of the well log and rock physic model was correlated with seismic inversion volume in terms of the lithology and porosity. Consequently, some zones which included carbonate tidal channel, displays a wide range of porosity and lithology fluctuations due to the impact of depositional environment (subaerial exposure).
The workflow provided insight into the distribution of petro-physical properties and quantification of their influence on dynamic reservoir behavior. The results also indicated the areas of high permeability and its component that may include fractures or connected vug systems. Water flood design and completion strategies (well trajectories) will be developed and succeeded according to the heterogeneous geological regions. Overall, this will ultimately lead to improve the development plan of wells in terms of production performance, recoverable reserves and economic value.
Hussein, Ali Hussein (Kuwait Oil Company) | Al-Khaja, Mohamed Jassem (Kuwait Oil Company) | Al-Menayes, Fahad (Kuwait Oil Company) | Al-Haddad, Hasan (Kuwait Oil Company) | Malik, Abdullah Ahmad Ali (Kuwait Oil Company) | Durge, Ashutosh (Kuwait Oil Company) | Dashti, Reham (Kuwait Oil Company) | Abdelaziz, Rami Mahmoud (Impact Fluid Solutions) | Barsoum, Victor (Impact Fluid Solutions) | Abdul Aleem, Bahaa (EMEC Kuwait) | Samak, Mohamed (EMEC Kuwait)
Wellbore instability while drilling mechanically weak, unstable or vugular formations has been a problem for decades. The cost of wellbore instability is a major challenge in achieving safe and economical drilling operations. As drilling operations moved into challenging formations in Kuwait, the operator sought to drill the Burgan shale and Shuaiba limestone formations in one section as opposed to the traditional two sections required to isolate each formation separately. This paper focuses on a class of technology additives used to mitigate the challenges of drilling weak and unstable formations.
One approach for drilling micro-fractured shale and weak sands with vugular limestone is to mitigate the invasion of drilling fluids into the formation. Other approaches include: stabilizing the reactive shale by preventing hydration and swelling, improving the filtercake texture and strength, and sealing natural micro-fractures. Drilling fluid invasion can change the pore pressure, which may trigger wellbore instability problems. Thus, using ultra-low invasion drilling fluids, sealing micro-fractures and maximizing shale inhibition are key components for mitigating wellbore instability. Field data for the wells using the ultra-low invasion additives and shale stabilizers is presented and compared with previous wells drilled across Burgan and Shuaiba formations in Kuwait.
The field data demonstrates the successful application of these additives to meet challenging key performance indicators (KPI) when drilling the Burgan shale and the vugular Shuaiba limestone in the same hole section. Using the ultra-low invasion additives along with shale inhibitors and borehole stabilizers, resulted in successful drilling operations with no differential sticking, torque-and-drag issues, sloughing, or tight hole problems as compared with usual incidences of differential sticking, pack-offs, and tight hole in other wells within the area. Using those additives also eliminated the need for a higher density fluid to control micro-fractured and tectonically stressed shales. The addition of the additive combination did not affect the rheological profile of the drilling fluid. Meeting these goals through the use of chemical additives in the drilling fluid reduced both non-productive time and formation damage in a cost-effective manner.
Data from this paper specifically addresses a chemical solution for drilling the Burgan shale formation together with vugular Shuaiba limestone in a major Middle East producing field. However, the technique of mitigating wellbore instability by using this combination of chemical additives is fundamental to safe and economical drilling operations for any depleted, weak or micro-fractured formations globally.
Dhote, Prashant Dhote (Kuwait Oil Company) | Al-Bahar, Mohammad (Kuwait Oil Company) | Cole, Anthony (DeGolyer and MacNaughton) | Al-Sane, Amal (Kuwait Oil Company) | Bora, Anup (Kuwait Oil Company) | Sreenivasan, Ashique (Kuwait Oil Company)
Residual Oil Zones (ROZs) are an area of incrasing attention from hydrocarbon E&P industry with ever depleting reserves in known oil accumulations and advent of Carbon Dioxide (CO2) Capture and Storage needs and technology. ROZ can serve as viable solution to both the future problems as a possible vast new oil resource and a prospect for reducing carbon emission. ROZs can be defined as thick pile of low-quality reservoir rock below traditional oil-water contact with about residual oil saturations of mainly irreducible oil resulting from the natural flushing of reservoir due to buoying forces and aquifer action in geological past in earlier oil-filled part of reservoir. The production of oil from ROZs from such reservoirs is technically and economicaly feasible through application of enhanced oil recovery techniques - largely through missible CO2 flooding/injection in the zone because of the nature of fluid and reservoir rock. The depostional and tectonic regime in the Kuwait Petroliferous Basins is investigated to demonstrate the occurrence of and independently assess ROZ potential. The understanding of Kuwait Petroliferous Basin indicates that ROZs might be developed by hydrodynamic actions associated with tectonic regime. The degradation of oil by water action and related increase of sulfur content of crude oil can be used as workable proxy for identification ROZ potential of the rerservoir. The regional mapping, understanding of tectionic history and regional systhesis of crude oil composition shows an extensive stratigraphic and lateral existence of ROZ potential across the Kuwait Petroliferous Basin.
This study aims to provide strategic roadmap and detail data acquisition program that will reveal ROZ production potential in Kuwait for Kuwait Oil Company (KOC).
The objectives of the paper are to use the Basrah NGL gas processing project in the Basrah Gas Company JV (BGC) to demonstrate best practice application of industry solutions and appropriate technology selection, aligning with project value drivers whilst managing technical and non-technical uncertainties in decision making.
In mid-2018 contracts were awarded for the Basrah NGL gas processing hub in Southern Iraq that will set the competitive cost and schedule benchmark for new gas plants in Iraq. Embracing Shell and industry experience to deliver a standardized and replicable design was a key priority for the project team and JV partners. Technology selections were evaluated against project value drivers to support robust decision making for current and future operations, and contracting strategy selected considering synergies across the portfolio through bundling and building on in-country experience.
Two trains of 200 mmscf/d each have been awarded in the first development phase, however future expansion requirements are much simplified with the facility designed to be expandable to 5 replicated trains providing a total 1000 mmscf/d capacity in line with the upstream gas production forecast. The benefits of standardisation and replication lock in further cost and schedule savings for subsequent gas processing trains and continue to lower unit development and operating costs. In line with the future plans for the facilities, pre-investments were made for major infrastructure investments including gas and LPG export pipelines and high voltage power supply.
The BGC NGL processing train design is flexible to the range of gas qualities prevalent in Southern Iraq. Technology selections have been appropriately made to consider current and future requirements both in terms of ethane and LPG recovery but also acid gas removal and Sulphur recovery solutions. In the case of Sulphur recovery, a Shell and-Paques developed, Thiopaq technology is selected to provide the most capital efficient flexible solution, whilst also providing ease of scale-up to higher recovery rates as the upstream gas supply becomes progressively more sour (with higher H2S content) over time.
This work presents the use of pre-stack simultaneous inversion and geostatistical inversion techniques for the delineation of Ratawi and Minagish reservoirs of North West Kuwait (NWK). The Ratawi and Minagish formations of Lower Cretaceous age proved to be hydrocarbon plays in Kuwait. The Ratawi Limestone is hydrocarbon bearing in different parts of Kuwait and Minagish Formation is a prolific producer of hydrocarbon in southern Kuwait. Although, hydrocarbon potential of Ratawi and Minagish formations are yet to establish in the study area, however, during drilling of deeper wells, the high gas shows encountered in Ratawi and Minagish formations is a strong indication of possible hydrocarbon accumulation. In view of the high gas readings and oil shows in Lower Cretaceous, it was decided to put emphasis on this field by utilizing the spatial coverage of 3D seismic data.
Hence, the pre-stack simultaneous inversion technique employed on the study area and the attribute volumes comprises of p-impedance, s-impedance, vp/vs, lambda-rho, mu-rho, poison’s ratio and young’s modulus were calculated to explore the hydrocarbon potentiality of reservoirs. Although, the pre-stack simultaneous inversion has increased resolution for the gross reservoir scale, it had only limited resolution for thin beds. Hence, geostatistical inversion was carried out on the pilot area to meet the challenges to explore the hydrocarbon potentiality of the reservoirs.
Based on inversion results like porosity, vp/vs, young’s modulus, poisson’s ratio with conventional seismic attributes best locations were identified targeting the Ratawi and Minagish formations. Very recently drilled well: F flowed from the Ratawi Limestone and Minagish Formation as predicted from the inversion results.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: 209A (Anaheim Convention Center)
Presentation Type: Oral
The 16″ Vertical Performance Motor Section is the most challenging section in Exploration Deep Drilling in Burgan Field & All South East Kuwait. The section comprises drilling hard and abrasive Zubair formation followed by reactive Ratawi Shale formation. Several technologies were introduced during the last ten years in search of an economic solution to deliver this section safer and faster with limited success. The objective of this paper is to present the process and technology implemented to drill Zubair and Ratawi Shale formations in two different wells with the same bit at record rates of penetration.
Bit durability is generally the main driver in the 16″ section performance. Historically, one to two polycrystalline diamond compact (PDC) bits were utilized in this section and were pulled out for low penetration rates. The new solution required a thorough offset data analysis, including formation porosity, rock strength and abrasiveness analysis, applied drilling parameters and Mechanical Specific Energy (MSE) analysis using software. A customized PDC bit design was then developed using a state of the art bit/formation interaction model combined with an advanced cutter technology and hydraulics pairing for ultimate cutter cooling.
The new PDC bit design and the implementation of the softwares used to analyse offset wells drilling parameters and rock mechanics had a significant effect on the bit durability and Rate of Penetration (ROP). The optimized drilling parameters applied as per the former set roadmap aided in managing the bit cutting structure through Zubair and Ratawi Shale formations and the bit was pulled out in re-runnable condition with a new field ROP record. The same bit was then used again in different well and drilled Zubair and Ratawi Shale formations and pulled out with 1, 3 dull condition. Over the two wells drilled, the optimized drilling plan saved National Oil Company over US $200,000, reducing the cost per foot (CPF) drilled by 38% over the field average CPF, increasing the ROP by 55% over the field average and drilling 69% footage more than the previous section benchmark footage.
With the engineering evaluation of the offset data and the utilization of the new bit design, National Oil Company managed to drill Zubair and Ratawi Shale section in two different wells with the same bit for the first time and was able to improve drilling efficiency and cutting the drilling cost by eliminating bit trips and cost of new PDC bits.