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Collaborating Authors
Ajienka, J.A.
Abstract Joint venture agreement and Production sharing contract are the two most common fiscal systems for petroleum operations in Nigeria. In this study, models were developed and compared for Joint venture agreement (JVA) and Production sharing contract (PSC) for the Nigeria fiscal systems. The results showed that the government has more take and a higher NPV under the JVA than the PSC. Sensitivities were carried out for the NPV and the results showed that NPV was most sensitive to oil price. An approach was also developed, based on the percentage loss in NPV of the contractor and community take, that serves as a guide for the contracting firms and JVA partners to determine how much should be given to the host community in such a manner that will not significantly affect their NPV and yet achieve their social responsibility. Introduction The global replacement rate of reserves over the past three decades is about 183 percent. That of Nigeria over the same period is about 200 percent which compares favourably. Thus the state of the upstream industry in Nigeria obviously portrays a high and optimistic look (Iledare 2004). However, the manner in which the Exploration and production activity is funded and the prevalent fiscal system, in no little way, affects this optimism. This is very significant and worth considering because of the importance of crude oil to Nigeria's economy. Over the past three decades, petroleum has been the key driver of the Nigerian economy accounting for about 80 percent of the government revenues and averagely 90โ95 percent of its foreign exchange earnings (Iledare 2004). The terms of the two fiscal regimes are different and consequently has an impact on the profit generated for the government and the oil companies. Two economic models for the two popular fiscal systems used in Nigeria were built- PSC and JVA. These models were built for different possible locations and applicable royalties using the National Petroleum Investment Management services (NAPIMS) classification as a base. A comparative economic evaluation of the two fiscal system was made. It quantified this comparison to show which yields more profit for the oil companies and the government. With the current unrest and clamour in and for the development of Niger Delta, there is a need for the operating E&P companies to wake up to their responsibility of being a socially responsible citizen if they intend to maintain a good name and carry on with their activities in a safe, peaceful and encouraging atmosphere. This can be achieved by making available funds that is used to develop the environment of their host communities in line with the community needs.
- Research Report > New Finding (0.88)
- Overview (0.54)
Abstract Hydrates and paraffin wax deposition are major flow assurance issues of concern in oil and gas production particularly in offshore operations. Thermal insulation is an attractive measure for preventing hydrate and wax deposition. In this study, a simplified Microsoft Excel Based program was developed for evaluating the effectiveness of thermal insulation in preventing deposition within the tubing when various insulating materials are placed in the tubing-casing annulus as replacement for completion brine. The effects of flowrate and tubing size were also analyzed. The study was performed by modeling steady state and transient heat transfer within the production tubing for both producing and shut-down conditions. Comparatively, most of the insulation systems considered gave better performance than completion brine. This effect was more significant at low flowrates. It was found that the most effective insulating materials for preventing heat loss and solid deposition during flow conditions do not necessarily possess good insulation characteristics in shut down conditions. Incorporation of flow assurance issues during completion design can have great impact in reducing incidence of hydrates and paraffin wax deposits. Introduction The huge capital investments incurred in oil and gas exploration and development can only be justified when the oil is produced at optimal rate and minimum cost. However, achieving this is no mean feat as development activities in the industry face significant challenges. Flow assurance issues have gained prominence amongst issues of concern in the industry because of their potential to disrupt production and increase production cost. Particularly worrisome is the effect of produced hydrocarbon solids such as wax and hydrates, which plug up perforations, tubings and flowlines, creating restrictions in the flow path, additional pressure drop and sub-optimal production conditions (Kabir et al., 2002). The precipitation and deposition of hydrocarbon solids occur within the wellbore and along flowlines when multiphase flow experiences pressure and temperature decline as the oil or gas is being transported. Occurrence of these deposits is also affected by other parameters such as the Gas Oil Ratio (GOR), Basic Sediments and Water (BS & W) (Ezeokeke, 2005). Each type of deposit has specific pressure-temperature equilibra and/or combination of parameters that would promote precipitation.
- Well Completion > Completion Installation and Operations (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Facilities Design, Construction and Operation > Flow Assurance > Hydrates (1.00)
Abstract The orifice discharge coefficient (CD) is the constant required to correct theoretical flow rate to actual flow rate. It is known that single phase orifice models and methods of prediction of critical flow do not apply to multiphase flow. Thus the questions that must be answered are how do we determine values of discharge coefficient for multiphase flow metering? Can the values of discharge coefficient for critical multiphase flow be used for subcritical flow? Figures, tables and equations of CD are presented with which metered multiphase flow rates can be corrected to obtain actual multiphase flow rates for both critical and subcritical flows. It is shown that CD for multiphase critical flow cannot be the same for multiphase subcritical flow. Introduction Multiphase flow is a complex phenomenon: As a result the majority of published correlations are highly empirical. This affects the general validity of these correlations for all ranges of fluid properties as they are limited to the quality and scope of the data base from which they are developed. Therefore, correlation which performs well within the range of data used to develop it, may fail outside this range. Multiphase flow through restrictions is usually evaluated under critical or subcritical flow conditions. As a standard oilfield practice, wellhead flow performance is evaluated under critical flow while flow performance through subsurface chokes and safety valves is done through subcritical flow. Critical or sonic flow is flow in which downstream pressure and temperature perturbations are not transmitted upstream to affect the flow rate unlike in subcritical flow. Available critical multiphase orifice flow correlations can be categorized as follows:Analytical models, applying mathematical analysis based on fundamental principles, to a simplified physical model with the development of equations. Empirical correlations using dimensional analysis to select and group the most important variables. Empirical correlations from field or laboratory data. Examples of category 1 correlations are those of Tangren et al., Ros, Poettmann and Beck, Ashford, a generalized model by Ajienka and Ajienka and Ikoku. The simplified form of the generalized model applicable to both continuous liquid phase flow and continuous gas phase flow is given by Equation (1): Equation (1) (Available In Full Paper) where Equation (2) (Available In Full Paper) Equation (3) (Available In Full Paper) Equation (4) (Available In Full Paper) Letting Equation (Available In Full Paper) To be equal to X, then: Equation (5) (Available In Full Paper) Equation (6) (Available In Full Paper) Flow is critical if the pressure ratio (X = Xc) is equal to the critical pressure ratio. Otherwise, flow is subcritical. Ashford's analytical correlation for critical flow is given by: Equation (7) (Available In Full Paper) where Equation (8) (Available In Full Paper) Equation (9) (Available In Full Paper) Equation (10) (Available In Full Paper) While the earlier analytical models assume that critical flow TABLE 1: Empirical coefficients of category 3 correlations. (Available in full paper) Occurs at a constant pressure ratio of 0.554 (for k = 1.04) as with single phase flow, the Ajienka and Ikoku model uses a predicted critical pressure ratio which is realist
- North America > United States > Louisiana (0.25)
- Asia > Middle East > Israel > Mediterranean Sea (0.25)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Multiphase flow (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Downhole and wellsite flow metering (1.00)