Although a large volume of mudcake filtration test data is available in the literature, effects of mudcake on wellbore strengthening cannot be quantified without incorporating the data into a stress-analysis model. Tr...Although a large volume of mudcake filtration test data is available in the literature, effects of mudcake on wellbore strengthening cannot be quantified without incorporating the data into a stress-analysis model. Traditional models for determining fracture initiation pressure （FIP） either consider a wellbore with an impermeable mudcake or with no mudcake at all. An analytical model considering permeable mudcake is proposed in this paper. The model can predict pore pressure and stress profiles around the wellbore, and consequently the FIP, for different mudcake thickness, permeability, and strength. Numerical examples are provided to illustrate the effects of these mudcake parameters. The results show that a low-permeability mudcake enhances FIP, mainly through restricting fluid seepage and pore pressure increase in the near- wellbore region, rather than by mudcake strength. Fluid loss pressure （FLP） should be distinguished from FIP when a mudcake is present on the wellbore wall. Fracture may occur behind the mudcake at FIP without mudcake rupture. The small effect of mudcake strength on FIP does not mean its effect on FLP is small too. Mudcake strength may play an important role in maintaining integrity of the wellbore once a fracture has initiated behind the mudcake.展开更多
A well-known but erroneous notion of electron degeneracy pressure has misled Astrophysics for nearly a century now. Because of their electrostatic interactions, the electrons can never exchange their momentum with pos...A well-known but erroneous notion of electron degeneracy pressure has misled Astrophysics for nearly a century now. Because of their electrostatic interactions, the electrons can never exchange their momentum with positive ions through elastic collisions and hence can never provide the so-called electron degeneracy pressure in stellar cores to counter the effect of gravity. In situations of high core densities, when the mean separation distance between atoms or ions becomes less than the normal size of their parent atoms, their electrostatic repulsion will force them into a lattice gridlock, leading to a solid state. All degenerate stellar cores constitute a solid state and the radial and hoop stresses induced by self-gravitation are proportional to the square of radius (r<sup>2</sup>). As the size of a solid iron stellar core grows, its peripheral region will experience extreme compression and will get partially ionized due to the phenomenon of pressure ionization. All so-called Neutron Stars and Black Holes are in fact Ionized Solid Iron Stellar Bodies (ISISB). The presence of ions in the peripheral regions of the ISISB will be associated with the circulation of degenerate electrons around the surface, thereby producing strong magnetic fields. A positive excess of ionic charge in all ISISB becomes a source of Ionic Gravitation through the process of polarization of neutral atoms and molecules in stellar bodies. These ISISB are the primary constituents of AGN and are the source of all non-stellar radiation and Jets of ionized matter.展开更多
基金the Wider Windows Industrial Affiliate Program,the University of Texas at Austin,for financial and logistical support of this workProgram support from BHP Billiton,British Petroleum,Chevron,Conoco Phillips,Halliburton,Marathon,National Oilwell Varco,Occidental Oil and Gas
文摘Although a large volume of mudcake filtration test data is available in the literature, effects of mudcake on wellbore strengthening cannot be quantified without incorporating the data into a stress-analysis model. Traditional models for determining fracture initiation pressure （FIP） either consider a wellbore with an impermeable mudcake or with no mudcake at all. An analytical model considering permeable mudcake is proposed in this paper. The model can predict pore pressure and stress profiles around the wellbore, and consequently the FIP, for different mudcake thickness, permeability, and strength. Numerical examples are provided to illustrate the effects of these mudcake parameters. The results show that a low-permeability mudcake enhances FIP, mainly through restricting fluid seepage and pore pressure increase in the near- wellbore region, rather than by mudcake strength. Fluid loss pressure （FLP） should be distinguished from FIP when a mudcake is present on the wellbore wall. Fracture may occur behind the mudcake at FIP without mudcake rupture. The small effect of mudcake strength on FIP does not mean its effect on FLP is small too. Mudcake strength may play an important role in maintaining integrity of the wellbore once a fracture has initiated behind the mudcake.
文摘A well-known but erroneous notion of electron degeneracy pressure has misled Astrophysics for nearly a century now. Because of their electrostatic interactions, the electrons can never exchange their momentum with positive ions through elastic collisions and hence can never provide the so-called electron degeneracy pressure in stellar cores to counter the effect of gravity. In situations of high core densities, when the mean separation distance between atoms or ions becomes less than the normal size of their parent atoms, their electrostatic repulsion will force them into a lattice gridlock, leading to a solid state. All degenerate stellar cores constitute a solid state and the radial and hoop stresses induced by self-gravitation are proportional to the square of radius (r<sup>2</sup>). As the size of a solid iron stellar core grows, its peripheral region will experience extreme compression and will get partially ionized due to the phenomenon of pressure ionization. All so-called Neutron Stars and Black Holes are in fact Ionized Solid Iron Stellar Bodies (ISISB). The presence of ions in the peripheral regions of the ISISB will be associated with the circulation of degenerate electrons around the surface, thereby producing strong magnetic fields. A positive excess of ionic charge in all ISISB becomes a source of Ionic Gravitation through the process of polarization of neutral atoms and molecules in stellar bodies. These ISISB are the primary constituents of AGN and are the source of all non-stellar radiation and Jets of ionized matter.
