J.A. Ajienka

Waxy Crude Oil Handling in Nigeria: Practices, Problems, and Prospects

Abstract With case studies, the practices, problems, and prospects of handling waxy crude oils in Nigeria are discussed. Using a rotational viscometer, the temperature dependence of Theological properties and thixotropy of these crudes were determined. Suggestions are given on how to improve handling practices. These suggestions include adequate screening and ranking of wax inhibitors, taking into account pour-point depression, viscosity, and yield value. Rheological studies would help in pipeline design and handling methods. A thorough knowledge of the nature of the crude oil at the time of discovery would help in the design of well completion and production facilities to optimize production.

Criteria for the design of waxy crude oil pipelines: maximum pump (horsepower) pressure requirement

Abstract A new approach to the design of power-law crude oil pipelines is presented. This method is based on the maximum pressure required in the handling of the power-law crude for normal uninterrupted flow, restarted flow and pressure to break the gel. The method is iterative as the rheology of power-law crudes is highly temperature dependent. This method is an improvement of the conventional oil pipeline design model. Using this criterion and the conventional method, a waxy crude oil pipeline in the Niger Delta was sized. The results show, among others, that the diameter predicted by this method is smaller than that of the conventional method. Also, for the same diameter the pump capacity and restart pressure requirements of this method are lower.

Application of mass balance of kick fluid in well control

Abstract A material balance equation of kick fluid in the annulus is derived. This equation can be used to determine the pressure head of the kick, whether or not the kick is intermittent or a continuous slug, the volume (or length) of the kick, the rate of rise of the kick fluid, the maximum casing pressure that will be encountered during the well control operation and the annular pressure as the kick reaches critical points of interest such as the casing seat. When integrated with transient surface shut-in drill stem test analysis techniques, pertinent formation characteristics can be evaluated. These can be useful for optimizing the planning, design and drilling of subsequent wells within the particular field. The model requires a minimum of assumptions and it is dynamic as it is based on the well control process. With speedy and accurate acquisition of the kick data, well control can become more efficient. The major limitations of the model include possible leakages in the flow system and high gas solubility in the drilling fluid. The procedure for the application is discussed and examples of a gas kick and a saltwater kick illustrate the applicability of the model.

Measurement of dielectric constant of oilfield emulsions and its application to emulsion resolution

Abstract The trial-and-error method of choosing an optimum demulsifier out of a wide variety of demulsifiers to effectively treat a given oilfield water-in-oil emulsion is time-consuming. To minimize this, the use of the dielectric constant as a criterion for screening, ranking and selection of demulsifiers for emulsion resolution was investigated. Dielectric constants of emulsions and demulsifiers were measured using a portable capacitance meter (Harris Model), while bottle tests were conducted according to API specification. The results show that the dielectric constants can be used effectively to screen and rank demulsifiers while a confirmatory bottle test is conducted on the best demulsifiers to assist in the rapid selection of the most effective demulsifiers. This procedure will save time and cost in the petroleum industry. On the basis of this study, a stage-by-stage screening procedure is presented.

Prediction of fluid flow parameters in a gas-cut mud, 2. Mathematical approach to the determination of the rate of gas bubble rise in a gas-cut mud

Abstract A mathematical relation is developed in this paper which is used to determine the rate at which a bubble of gas, cut in mud, migrates to the surface. The maximum time for the bubble to reach the surface can also be estimated from the equations. Application of field data to the equations confirm that the rate at which gas migrates to the surface increases with decreasing pressure and temperature.

Predictive Models for Condensate Gas Ratio (CGR) – Part 1: For Western Niger Delta Region

Condensate-to-gas ratio (CGR) playsa significant role in sales potential assessment of both gas and liquid, design of the required surface processing facilities, reservoir characterization and modeling in gas -condensate reservoirs.This work aim at the use of regression method to develop Condensate gas ratio (CGR) correlations using dataset obtained from Western Niger Delta region. The formation was divided into three distinct geologic zones: Transitional Paralic, Paralic and Marine Paralic zones. The basic parameters used for the correlatio n development are: reservoir depth (ft), reservoir pressure (psia); reservoir temperature ( o

Oilfield Production Surveillance as a Management Tool for Environmental Monitoring

Oilfield production surveillance is the effective monitoring of petroleum reservoirs, producing wells, flow station facilities and flow lines. Through surveillance, the production of unwanted effluents (formation water, excess gas, etc.) can be controlled. Production problems such as sand production, emulsion, corrosion, scale formation and wax blockage can lead to disposal problems and poor integrity of facilities and consequent financial losses. This paper presents a system approach for carrying out oilfield production surveillance process. Using case studies it is shown that the process can be used to identify unfavourable conditions such as gas leaks, corrosivity, and unsafe wells. It is further recommended that the frequency of surveillance should be monthly

Effects of Inflation and Time Value of Money on Drilling Optimization

Abstract The cost per foot relationship is one of the most popular objective functions used in drilling optimization. Its major applications include monitoring the cost-effectiveness of drilling a number of wells in a given field in such a way as to determine the optimum cost per foot in that field, comparison of drilling efficiency in the development of a new field against offset field, and in break-even analysis of bit performance. In doing these, operators very often neglect the effects of inflation and time-value of money. In this article a discounted cost per foot is computed that accounts for both inflation and time value of money. An example is given to illustrate the applicability of this concept.