The constant al primarily represents the effect of formation strength on penetration rate. It is inversely proportional to the natural logarithm of the square of the drillability strength parameter discussed by Maurer. 2 It also includes the effect on penetration rate of drilling parameters that have not yet been mathematically modeled; for example, the effect of drilled solids.
An industry and academic standard, Applied Drilling Engineering presents engineering science fundamentals as well as examples of engineering applications involving those fundamentals. Two appendices are included, along with numerous examples. Answers are included for every end-of-chapter question. Solutions to Chapter 8 (http://go.spe.org/ADEsolutions)
A large number of producing wells in the OCS develop undesirable and sometimes potentially dangerous sustained pressure on one or more casing strings of completed wells. This paper examines the severity and frequency of the occurrence of sustained casing pressure in the offshore Gulf of Mexico area. Possible causes for this problem are discussed and case histories of remediation techniques being tried by offshore operators are presented. Introduction The invention of portland cement by Joseph Aspdin has allowed major advances in our civilization because of its low cost, strength, and ability to set under water. It has been modified and used by the oil and gas industry since the early 1900's as the primary means of sealing the area between the open borehole and the casing placed in the well. Shown in Figure 1 is a typical well completion showing the placement of cement to seal off the interior of various casing strings from the subsurface formations exposed by the drill bit. Ideally, the well of Figure 1 should show pressure only on the production tubing. Gauges on all of the casing strings should read zero if:the well is allowed to come to a steady-state flowing condition, andthe effect of any liquid pressurization due to heating of the casing and completion fluids by the produced fluids is allowed to bleed off by opening a needle valve. Only a small volume of fluid generally has to be bled in order for the casing pressure to fall to atmospheric pressure if the pressure was caused by thermal expansion effects. If the needle valve is closed and the well remains at the same steady-state condition, then the casing pressure should remain at zero. If the casing pressure returns when the needle valve is closed, then the casing is said to exhibit sustained casing pressure (SCP). In some cases the pressure can reach dangerously high values. The Minerals Management is concerned about wells on the Outer Continental Shelf (OCS) that exhibit significant sustained casing pressure because of its responsibility for worker safety and environmental protection as mandated by congress. At present, any amount of sustained casing pressure seen on one or more casing strings of a well (excluding drive pipe and structural casing) is viewed as significant enough to trigger notification of MMS. Structural and drive pipe are excluded because it is recognized that gas of biogenic origin is sometimes encountered in the shallow sediments and can cause insignificant pressures on the drive and structural casing. SCP also triggers a requirement that records of the casing pressures observed be kept available for inspection in the operator's field office. Regulations under 30 CFR 250.517 state that the lessee shall immediately notify the MMS District Supervisor if sustained casing pressure is observed on a well. A written record of notification must be placed in the operator's SCP records by close of business the next working day after the SCP is discovered. If the well is felt to be in an unsafe condition, the district supervisor can order that remedial actions be taken. However, provisions are made for a departure from 30 CFR 250.517 to be obtained.
When drilling from a bottom supported structure, the best procedure for handling a threatened blowout from a shallow gas formation is to divert the gas flow away from the structure and drilling personnel. Case histories were reviewed in which failures occurred during diverter operations due to erosion caused by sand production. A model diverter system was constructed to evaluate this problem and provide information that can be used in the design of diverter systems. A number of pipe fittings used at bends in diverter systems were experimentally evaluated. The effect of flow velocity, liquid content, and sand concentration were included in the study. It was found that very rapid wear can occur at velocities near sonic velocity. Wear rates of 8-in./hr were measured for short radius "Ells." The rate of erosion was found to be about two orders of magnitude higher for gas/sand mixtures than for liquid/sand mixtures. An equation was developed for predicting the wear rate for various field conditions. Recommendations are given for improving the erosion resistance of diverter systems.
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