There is an increasing need to limit the use of chemical treating agents during oil and gas production and to search for safer and cost effective ones mainly due to environmental constraints. Therefore the use and performance of demulsifiers have to be improved from the application and cost as well as from the environmental issues. This means that new formulations must be less toxic and efficient compared to the general classical chemical families of demulsifiers which contain toxic molecules like phenol groups. This paper is on the performance and the comparison of four chemical demulsifiers (local and foreign) on their demulsification of four crude oil emulsions of different asphaltene contents from different oil wells in the Niger Delta. The chemical families of these demulsifiers were screened with effective separation ability of different surfactants using classical "Bottle test". The Bottle test helped to determine the type of demulsifier that will most effectively break the emulsion of the crude samples. The basic aim of this screening was to compare and rank the efficiency of the various demulsifiers both local and foreign (V4404 of Nigeria, 92LTM174 of USA, EN/82/2 of France and DS 964 of Canada) in terms of percentage (%) volume of water that will be separated out of the samples. The results showed that the viscosity of the emulsions increased as the water content increased with an assumption that only oil and water were present. The nature of the emulsions were subject to changes, therefore no treatment method was conclusively generalized as best for every emulsion problem. Finally from the preliminary screening, the result also revealed that V4404 a local demulsifier exhibited very interesting performance and was also environmentally friendly compared to the imported ones.
Sand production is described as the production of load bearing sand grains along with the produced reservoir fluids. Problems associated with it include: blockage of tubular, formation damage, casing collapse, erosion of facilities, leakages and spills, environmental issues and disposal problems. Predicting the potential of sand incidence is an important decision that petroleum engineers must make, at the time of well completion to avoid unnecessary sand control expenses. In this work, a parametric study was made to investigate the impact of various mechanical rock properties using Omar Abdulaziz Almisned's prediction model. Different diagnostic plots were made to establish unique trends for five cases using five different rock parameters and compared with the critical pressure at various depths. It was observed that the critical pressure increases with the increase in Shear modulus, Young's modulus and bulk compressibility, but decreases with the increase in poisson's ratio and bulk modulus. In addition, it was observed that the plot, (1/k)/(ts/tc)x10 10 , gave a close and consistent trend. This parametric combination has the same dimension as rock compressibility. This model will serve as a useful tool to estimate critical well pressure causing sand prediction, predict sand production and can also be used to perform parametric comparison of different mechanical rock properties.
One of the major challenges of drilling and completion of oil and gas wells is the uncertainty in the formation fracture gradient and the fracture pressure. It is not uncommon that many drilling companies have spent money, resources and time in drilling and completing wells that should have been simply and optimally done. Fracture gradient evaluation constitutes one of the essential parameters in the pre-design stage of drilling operations, reservoir exploitations and stimulations. Several calculation methods and computer models have been presented in the literature for different regions of the world. Most of these techniques were based on either parametric or empirical correlations, which required a prior knowledge of the functional forms or the use of empirical charts which were not very accurate. This paper presents an innovative method of predicting formation fracture gradient for Gulf of Guinea region. A combination of "Mathew and Kelly" correlation, "Hubbert and Willis" correlation and Ben Eaton mathematical models were used in developing the simplified technique based on field data from the Gulf of Guinea. The model compared favorably with the existing fracture gradient results in the Gulf of Guinea with less than 1 % deviation from other correlations thereby saving the rigors and time in using tables, charts and other long techniques. Although the method was developed specifically for the Gulf of Guinea, it should be reliable for other similar areas provided that the variables reflect the conditions in the specific area being considered.
It is very important to design a stable mud system for any detailed drilling programs. Application of the best practices and well planned engineering field execution is critical in drilling and completing HPHT wells in a cost effective manner and minimal operational problems. Conventional mud designs and test equipment fell short of addressing the inherent problems associated with HPHT wells. In this study, the conventional practices in mud design were reviewed and advances in design for best practices developed for Mafia field. Many of the conventional practices were actually found to be inadequate for HPHT drilling. This paper present techniques on determining and applying mud properties at HPHT deep wells through a rigorous laboratory test and mathematical equations to generate detailed engineering guidelines for HPHT drilling fluid. Water based mud were formulated with special additives at temperature between 250-500°F and 5,000-10,000 psi to check for its stability under such elevated temperature and pressure. A standard temperature concept used for controlling the surface mud weight was defined. With the actual field results from the Mafia field, model equations were developed and the sensitivity analysis done to show the relative influence of pressure and temperature on the drilling fluids using the spider and tornado plots. The model equations derived from the multiple regression analysis were used to predict and rank the best rheological properties for the field, thereby saving the time and rigors associated with laboratory experiments.
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