Geostatistical-based models provide a considerable improvement for predictive reliability of dynamic models and the following reservoir management decisions. This study focuses on geostatistical modeling the Paleocene Zelten Carbonate reservoir in the Meghil field. The field was discovered in 1959 and production operations began in 1961. Nineteen wells have been drilled to date. The structural framework consists of three slightly asymmetrical anticlinal structures trending NW-SE with steeper dip on the SW flanks. Each of the structures are separated by major normal faults. Seismic interpretation suggests that carbonate build-ups are most likely present on the three separate structures. Edge detection was used to clarify the structural geometries and the presence of additional minor faults. Pillar gridding technique was used to develop the structural framework including four major faults that are partially sealed based on analysis of the available DST and production test data. Stratigraphic analysis indicates a local presentation of dolomitic limestone in the northern portion of the main and the western structures caused considerable litho-facies variation that impacted the distribution of the petrophysical properties. Basic and advanced formation evaluation the net reservoir thickness of about 15 feet with an average porosity of 17% and average water saturation of 35%. Geostatistical-based applications that combine the spatial statistics (e.g. the semivariogram) and the available well and core data were used to populate the reservoir model with porosity, permeability, facies (lithology), net/gross, and water saturation. A conceptual facies model was also used to constrain the reservoir property distributions. Sequential Gaussian Simulation (SGS) was used to populate the model with porosity and water saturation and Sequential Indicator Simulation (SIS) was used to populate the facies model with permeability. The modeling parameters (e.g. semivariogram, correlation coefficients) were significantly constrained by the limited number of wells. Based on the limited number of wells available the semivariogram analysis resulted in a spherical semivariogram model with major axis range of 1435 meters for porosity and 1800 meters for water saturation. Minor axis ranges were about 50% of the major axis ranges. Given the limited well data, a significant effort was made to document the potential impact of the semivariogram parameters on the original hydrocarbon in place (OHIP) estimates and the lateral stratigraphic continuity of reservoir properties. The deterministic approach resulted in place volume estimates of 60 MMBBL and the stochastic approach provided an estimate of 45 MMBBL.
An SPE student chapter at Al-Fatah U. and a Young Professionals (YP) program have been established in Libya for the first time. The programs were created after a visit from 2006 SPE President Eve Sprunt with Ross Davidson, Director of Operations, SPE Office in Dubai. The 2006 YP Liaison and the Membership Chairpersons (Yosra Abugren and Piers Temple, respectively) accompanied Sprunt and Davidson in their visit to the students of Al-Fatah U.'s Petroleum Engineering Dept. They gave a presentation illustrating the importance and benefits of joining the SPE student chapter. The students were very enthusiastic about the visit and showed great interest in joining and becoming active members.
The SPE Libya Section has a fully functional student chapter at Al-Fateh University in Tripoli and a Tier 1 Young Professionals Section. A group of petroleum engineering (PE) students attended a specialized beam pumping training meeting in Tripoli presented by Lufkin, Norris, and Harbison Fischer. To share knowledge gained from the training with the rest of the PE students at the university, the chapter arranged a short beam pumping seminar by Professor Mohamed Ghareeb and engineer Nael Sadek. Participants discussed the applicability of beam pumps for Libyan wells and the use of automation techniques to acquire real-time data for monitoring and control.
Just as Libya resumes oil exports from recently shuttered ports, an attack on its largest field is setting back progress yet again. An incursion by gunmen into the Sharara field on 14 July and the kidnapping of workers there forced the National Oil Corp. (NOC) to cut output and ban exports. It’s the latest in a string of security incidents that have hobbled Libyan shipments despite repeated attempts to restore flows in the politically divided nation. The kidnappers released two of the four abducted workers later the same day but still hold two others. The persistent assaults on the OPEC state’s oil facilities show that any efforts to revive production remain hindered by the same security issues that have long plagued the industry.
ABSTRACT: Wellbore instability has been the primary cause of financial losses in boreholes in the drilling industry. Wellbore instabilities are responsible for 10-20% of the total drilling cost. It has been estimated that wellbore instability causes an annual economic loss of $ 1 - 6billion in the oil industry across the world. One type of these wellbore instabilities was a hole enlargement problem encountered in the J-NC186 Oil field located in southern of Libya. This paper examines one side to solve this problem. So a geomechanical wellbore stability analysis was implemented using Schlumberger Techlog software to effectively plan the future drilling operations in the field to maximize the drilling margin for the future wells drilled, and to optimize the future field development. 1-D geomechanical models show that the horizontal wells are more stable than the vertical ones. The models also show that drilling to the orientation of east-west can minimize the wellbore instabilities. The models suggested the optimum mud weight window to drilling the reservoir section safely, and represented the results using stereographic projection. The outcomes of this study can be utilized for further field developments for enhancement of the hydrocarbon production (e.g. hydraulic fracturing, open-hole completions, and enhanced hydrocarbon recovery).
Wellbore stability is a term used in the Oil and gas industry to describe usable condition of the borehole during drilling operations. A usable hole must successfully accommodate logging or any open-hole evaluation, casing run and any other drilling activities.The Oil and gas industry continues to fight borehole problems. The problems include: hole collapse, tight holes, stuck pipes, poor hole cleaning, hole enlargement, plastic flow, fracture, and lost circulation. Most of these borehole problems that drive up drilling costs are related to wellbore stability. These problems are mainly caused by the imbalance created between the rock strengths and induced stresses after wellbore drilling.
The petroleum systems of the Sirt Basin province were evaluated based on the burial history, thermal maturity and timing of the generation of oil and/or gas. These elements were modelled for the main petroleum source rock units at eight boreholes situated in the Sirt Basin province. The Sirt Basin petroleum systems can be divided into three main areas in the western region centred on Zellah Trough, Dor Al Abdi Trough and Marada Trough. Vitrinite reflectance (%Ro) was used to determine thermal history. Stratigraphic data, such as depth, thickness, lithology and age obtained from final or composite well logs were also used. This study, established that the petroleum system in the central and western part of the Sirt Basin is an Upper Cretaceous Petroleum System, which includes the Upper Cretaceous Campanian and Maastrichtian marine shale source rocks and Lower and Upper Cretaceous, Palaeocene and Eocene sandstone and carbonate carrier beds and reservoirs. Therefore, the central and western part of the Sirt Basin could be classified into two plays: the Upper Cretaceous and Palaeocene plays; and the Upper Cretaceous and Eocene plays. The presence of these plays is mainly because of the combination of a regional Upper Cretaceous source rock with a structural geometry created later by the Upper Cretaceous and Palaeocene syn-rift system and the Eocene to Oligocene post-rift system and its subsequent subsidence. Migration of the generated and expelled oil and gas from the Sirte Shale and Rachmat source rocks to the reservoirs of the Upper Cretaceous-Tertiary petroleum system was interpreted to have occurred along both vertical and lateral pathways along the faults, in the Oligocene to Miocene, while oil carbazole data indicated that this migration was generally likely to have been over relatively short distance.
Abdelnabi, Abdalla (Missouri University of Science and Technology) | Liu, Kelly (Missouri University of Science and Technology) | Gao, Stephen (Missouri University of Science and Technology) | Abushalah, Yousf (Uinversity of Texas)
Cambrian-Ordovician and Upper Cretaceous reservoir formations, the primary producing formations in the Sirte Basin, Libya have complex structures which affect the performance of the reservoirs. It is critical to understand the complicated relationships between fault networks, fractures, and stratigraphy of the area for future field development. However, detecting faults especially subtle faults and fractures is a challenging task using conventional seismic data due to the low signal-to-noise ratio. Seismic attributes provide effective tools in identifying and enhancing fault and fracture interpretation beyond the seismic resolution of the conventional seismic data. In this study, we focus on coherence and curvature attributes extracted from the post-stack 3D seismic data acquired in the central Sirte Basin to delineate subtle fault and fracture zones. We applied a median filter and spectral whitening to enhance the data quality and remove noise resulted from acquisition and processing effects. We utilized these methods to produce high-resolution data and preserve structural features. A total of 17 faults have been identified in the study area. The most common fractures in the Cambrian-Ordovician reservoir formations are in the northwest and southeast of the field. Seismic data conditioning and seismic attribute analyses applied on the 3-D seismic data effectively increased our understanding of the reservoir complex and help detect and identify subtle faults and fracture zones in the study area.
Presentation Date: Tuesday, September 26, 2017
Start Time: 9:45 AM
Location: Exhibit Hall C/D
Presentation Type: POSTER