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Well Construction: Drilling Fluid Functions

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Background Earlier on, we defined drilling fluid and attempted to classify them based on the nature of the basic fluid used in its formulation eg water based fluid, oil based fluid and pneumatic fluids. We also went further to group them into formation dispersant and non formation dispersant fluids. Then we talked about shale inhibition fluids. Extensive research and field results acquired during drilling operations had proven that penetration rate and its response to weight on bit and rotary speed depends on the hydraulic horse power reaching the formation at the bit. Since the drilling fluid flow rate sets the system pressure losses and these pressure losses set the hydraulic horsepower across the bit, it can be concluded that drilling fluid is very important in the determination of drilling cost. An optimum drilling fluid is a fluid properly formulated so that the flow rate necessary to clean the hole results in the proper hydraulic horsepower required to clean the bit for the weig...

Petroleum Exploration: Geology of petroleum reservoir rocks

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Introduction: Because the oil and gas well construction industry is diverse and involves people from differing technical and academic backgrounds, it will be necessary we explain basic geologic concepts and definitions with regards to the targets that the drilling of a well is supposed to reach. In the previous article, it was explained that the thermodynamic properties of petroleum is used to classify it into oil and gas. Oil then consist of higher order hydrocarbons with much smaller order of lower order hydrocarbons while gases consist of more of lower order hydrocarbons. Petroleum found at a condition above the bubble point pressure is all liquid or undersaturated. Below the bubble point, the petroleum is 2 phased or saturated. At considerable lower pressure and below the dew point pressure, petroleum are all in the gaseous phase. Petroleum is found mainly in sedimentary basins trapped by overlying impermeable closing rock. The aim of geological reconnaissance survey is to loca...