Bottomhole pressure, measurement

Implementation of an on-site computer control unit eliminates the need for mechanical systems, and enables real-time computation of bottomhole pressures. Monitoring techniques and pressure calculation methods vary extensively throughout the service industry. However, the measurable parameters such as surface treating pressure, liquid and gas injection rates, proppant concentration, and slurry temperature are the parameters that must be used to determine the bottomhole pressures. 

The bottomhole pressure of injection wells was determined according to the known barometric formula. However, for the gas wells a correction was made for the increase in gas density. The steam density was calculated to be 20-30% higher on account of the moisture content, and gas density was assumed to equal 0.7 of air density. Inasmuch as the pressure changes in the production-observation wells were not significant, the effects that the injection wells exerted mutually among themselves could be ignored. In other words, it was assumed that all injection wells operated independently of one another. Before the pressure field map was constructed, all pressures measured in the production-observation wells were brought up to the moment at which steam injection was discontinued. Visual extrapolation was used for that puipose. 

The bottomhole pressure histories were analyzed in the four producing wells. The values measured before injection were approximately constant. Therefore, the averages are considered to be baselines. Table 5 summarizes the pressirre behavior. For one well, the data collected show an increment approximately one month after injection began. For the other three wells, backwards data extrapolation suggests approximately two months. Most of the pressure increment ratios range between 1.7 and 2.7. 

Wehunt, C. D. 1990. Evaluation of alternating phase fracture acidizing treatment using measured bottomhole pressure. Paper SPE 20137, presented at the Society of Petroleum Engineers Permian Basin Oil and Gas Recovery Conference, Midland, TX. 

Figure 2-56 shows a plot of the theoretical maximum overburden pressure and the theoretical minimum pressure as a function of depth. Also plotted are various bottomhole fluid pressures from actual wells drilled in the Gulf Coast region [33]. These experimentally obtained pressures are the measurements of the pressures in the fluids that result from a combination of rock overburden and the fluid hydraulic column to the surface. These data show the bottomhole fluid pressure extremes. The abnormally high pressures can be explained by the fact that the sedimentary basins in the Gulf Coast region are immature basins and are... 

Plastic Viscosity and Yield Point. Plastic viscosity and yield point measurements are obtained from a direct indicating viscometer. Due to the temperature effect on the flow properties of oil-base mud, the testing procedure is modified. The mud sample in the container is placed into a cup heater [23]. The heated viscometer cup provides flow property data under atmospheric pressure and bottomhole temperature. 

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