Drilling history

Review of the drilling history (drilling reports) can reveal damage caused early in the life of a well. This includes an understanding of fluids used and their properties (oil based or water based, pH, solids used, etc.). There are two primary drilling damage mechanisms to consider ... 

Thixotropy and Other Time Effects. In addition to the nonideal behavior described, many fluids exhibit time-dependent effects. Some fluids increase in viscosity (rheopexy) or decrease in viscosity (thixotropy) with time when sheared at a constant shear rate. These effects can occur in fluids with or without yield values. Rheopexy is a rare phenomenon, but thixotropic fluids are common. Examples of thixotropic materials are starch pastes, gelatin, mayoimaise, drilling muds, and latex paints. The thixotropic effect is shown in Figure 5, where the curves are for a specimen exposed first to increasing and then to decreasing shear rates. Because of the decrease in viscosity with time as weU as shear rate, the up-and-down flow curves do not superimpose. Instead, they form a hysteresis loop, often called a thixotropic loop. Because flow curves for thixotropic or rheopectic Hquids depend on the shear history of the sample, different curves for the same material can be obtained, depending on the experimental procedure. 

Brandy, J. E. (1960). History of Oil Drilling. Houston, TX Gulf Publishing Co. 

Drilling surface data such as weight-on-bit and torque were difficult to interpret because they were loosely related to downhole values. MWD for the first time in the history of drilling gives values of parameters measured at the bit or close by. Rock strength, bit wear, drag and friction can be calculated in real time. Shocks, temperature and pressure can also be measured. 

Once wells have been drilled into the formation, the local properties of the reservoir rocks and fluids can be determined. To constmct a realistic model of the reservoir, its properties over its total extent— not just at the well sites—must be known. One way of estimating these properties is to match production histories at the wells with those predicted by the reservoir model. This is a classic ill-posed inverse problem that is very difficult to solve. 

D. Kinchen, M. A. Peavy, T. Brookey, and D. Rhodes. Case history Drilling techniques used in successful redevelopment of low pressure H2S gas carbonate formation. In Proceedings Volume, volume 1, pages 392-403. SPE/IADC Drilling Conf (Amsterdam, the Netherlands, 2121-m), 2001. 

M (276, 276) Rock drilling, stone crushing, stone dust — job/task history OR 2.2 (1.2, 3.9) Stolt39... 

Shackelton, N. J. Kennett, J. P. (1975). Paleotemperature history of the Cenozoic and the initiation of Antactic glaciation oxygen and carbon isotope analyses in DSDP Sites 277, 279 and 281. In Init. Rept. Deep Sea Drilling Project, pp. 743-55. Wahington D.C. U.S. Government Printing Office. 

The above P-T-t paths do not cover all temperature-pressure histories. For example, all deep-seated rocks may be brought up rapidly by volcanic eruptions as xenoliths and hence may cool from a high temperature to room temperature rapidly. Furthermore, through drilling it is possible to obtain samples at high temperatures and pressures. 

One way scientists have learned about the levels of carbon dioxide in the past is through the analysis of ice cores. An ice core is a tube of ice, usually drilled out of a glacier or ice sheet, that contains bubbles of air trapped inside layers of snow and ice. Each layer of snow and ice represents roughly a year. The deeper the layer, the older the ice sample. From the size and chemical content of each layer, scientists can draw conclusions about the temperatures at that point in history at that spot on the planet. At the same time, the bubbles of air preserved in each layer contain indicators of the amount of atmospheric carbon dioxide present at that time. 

Much of what is currently known about the Earth s climate comes from the application of stable isotopes collected from ocean drill cores in marine sediments (e.g., Zachos et al. 2001). These isotopic data sets provide detailed records of how the Earth s oceans have responded to changing climate and are extremely valuable in assessing global climate histories down to millennial scales. Similar detailed isotopic records for terrestrial systems are, however, uncommon and frequently continuous terrestrial climate records that span millions to tens of millions of years are not preserved in the terrestrial geologic record. With the advent of paleoaltimetry studies targeted directly at the coupled isotopic effects of changes in climate... 

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