International Journal of Petroleum Engineering (5 papers in press)
Using Well Logging Data to Predict Permeability of a Complex Formation
by Fadhil Kadhim, Ariffin Samsuri, Ahmad Kamal Idris
Abstract: One of the most challenging aspects of well log analysis is the accurate estimation of permeability in complex carbonate reservoirs. Permeability is predicted from many models by using well log data. Many correlations are developed over the years to calculate permeability based on known petrophysical properties or empirically derived relationships. The complex formation under study is Mishrif carbonate formation that is one of the shallowest hydrocarbons bearing zone in the Nasiriya oilfield in the south of Iraq. The available scanned copies of well logs are digitalized by using Neurolog software. Schlumberger charts 2005 had been used for environmental corrections. These correction charts are supplied in the Interactive Petrophysics software. The Schlumberger K3 and Timur models have been used to estimate permeability of Mishrif carbonate formation. After making the environmental corrections, the porosity interpretation shows that the logging tools have a good quality of data reading. From Schlumberger and Timur models, the permeability of Mishrif formation is ranged from 6.25 to 25.21 and 5.95 to 26.81 respectively. This study is provided permeability for varies depth, that is very important in the evaluation of the studied formation.
Keywords: Well Logging; Permeability; Complex Formation.
EXPLOITATION OF THIN OIL RIMS WITH LARGE ASSOCIATED GAS CAP
by A.G.I. AUGUSTINE
Abstract: Thin oil rims are reservoirs with thin oil column sandwich between water and gas layers, it occurs in reservoirs with high compacts sand, high porosity, high permeability and contain light crude. However, with this favourable reservoir conditions, maximizing oil production is a challenge. Even with good practices, a significant amount of oil column about 10+ft is left at abandonment. This research investigates the use of horizontal well with different completion scenarios to maximize oil recovery under the reservoirs prevailing natural energy. The research was based on extensive simulation studies conducted for several hypothetical cases, with varied petrophysical data. Oil recovery greater than 19% of the OOIP, with a high gas production of about 95% GIIP, and low water production of 8% was observed. Applying the Levenberg-Marquardt algorithm in the statistical data analysis, a recovery factor correlation was developed as a simple tool to evaluate the performance of thin oil rims, the recovery factor correlation was validated with publish data. Thus, it can be concluded from this hypothetical study that, the oil recovery from a thin oil rim reservoir with a large associated gascap increases as the horizontal permeability increases and decreases as the oil rate and horizontal well length increases. Moreover, the simulation studies also reveal that placing horizontal wells near the gas-oil contact is most likely the optimum production strategy for increasing oil recovery.
Keywords: Thin Oil Rims; Simulation; Enhance Oil Recovery; Design of Experiment; Levenberg-Marquardt.
A Brief Review of Mechanisms for Carbon Dioxide Sequestration into Aquifer Reservoirs
by ACHINTA BERA, Hadi Belhaj
Abstract: This paper presents a thorough understanding of carbon dioxide (CO2) gas sequestration mechanisms taking place at the time of injection, post injection and settlement of CO2 into the aquifer reservoirs. The paper also presents a broad model consisting of two positive components and one negative component to briefly describe the microscopic mechanisms that occur during CO2 trapping in aquifer reservoirs. The force of displacement (CO2 displaces water partially from the pore spaces) and the force of pore space enlargement to increase the storage capacity for CO2 (CO2 in contact with formation water produces carbonic acid acting as a stimulating agent for certain types of rocks) are the positive influencing factors for CO2 trapping in the aquifer reservoirs. On the other hand, the force of swelling is the negative component of the model (dissolved CO2 in formation water gives it more volume to consequently displace CO2 off the pore space). This short review will discuss the current scenario of understanding of CO2 trapping mechanisms, structural trapping mechanisms, kinetics of CO2 dissolution and future challenges and developments of carbon capture and storage (CCS) projects. Based on the information provided in this work, it is expected that the present study will be able to deliver a complete understanding of microscopic phenomena that happen during CO2 trapping into aquifer reservoirs apart from the existing mechanisms available in the literature.
Keywords: CO2 capture and storage; CO2 trapping mechanisms; Deep saline aquifer; Drainage; Imbibition; Swelling.
Evaluation and Optimization of Oil Wells on Plunger Lift in the Main Soldado Field Offshore the Southwest Coast of Trinidad A Theoretical Approach
by RAFFIE HOSEIN, Shazim Mohammed
Abstract: Plunger lift is an artificial lift technique that utilizes reservoir energy stored in the gas phase to lift oil from the bottom of the well to surface. In this study, plunger lift systems on two wells in the Main Soldado Field Offshore the Southwest Coast of Trinidad were evaluated to determine well performance using the Vogel model and to optimize oil production rates using the Foss and Gaul model. The mode of operation with the current setting is representative of intermittent lift with the assistance of a plunger rather than gas assisted plunger lift operation. The results obtained from the new settings showed that 61 % less gas is required to obtain 89 % more oil at optimum production rate. The evaluation described in this study can be used to effectively optimize gas assisted plunger lift systems for oil wells producing from this field.
Keywords: artificial lift; gas assisted plunger lift; well performance; optimize oil production; Vogel; Foss and Gaul; Trinidad.
OPTIMIZATION OF HYDRAULIC FRACTURE PLACEMENT DESIGN IN ANISOTROPIC SHALE RESERVOIRS USING AZIMUTHAL LWD SONIC AND SPECTRAL GAMMA RAY ANALYSIS
by Gbenga Oluyemi, Tomilayo Afolabi
Abstract: Hydraulic fracturing (fracking) of shale resources has become a trend in the oil and gas industry that is associated with exorbitant costs. This calls for certainty in the productivity and success of every fracture stimulation program. Current fracking practices rely mostly on a geometric design and evaluation of vertical well sections and pilot holes to predict properties along wellbore laterals. Consequently, there is a reduction in the efficiency of fracture stimulation programs and productivity of shale reservoirs. This problem is associated with the fact that shale reservoirs are anisotropic, possessing directional properties that cannot be accurately predicted as such. In order to increase the efficiency of fracture stimulation, considerations have to be given to the anisotropic tendencies of shale petrophysical and geomechanical properties along wellbore laterals where fractures are hydraulically induced. In this study, an approach for the accurate quantification of vertical transverse isotropy (VTI) and resultant anisotropic properties along shale wellbore laterals using an LWD azimuthal sonic log was investigated. Using the case study of a Marcellus shale well in Northeastern Pennsylvania having azimuthal sonic data, a work flow for obtaining anisotropic properties, critical to fracture stimulation design was developed. An algorithm for the characterization of wellbore geomechanical quality based on estimated VTI anisotropy, anisotropic closure stress and brittleness was also developed.
Keywords: Fracking; shale resources; anisotropy; stimulation; petrophysical properties; geomechanical properties.