Problems of Ultra-Deep High-Temperature, High-Pressure Drilling

Well Integrity for Natural Gas Storage in Depleted Reservoirs and Aquifers

“…Depth is an important factor to consider relative to wellbore integrity, because it is related to the likely potential pressure of the subsurface environment. Formation overburden pressure generally increases with depth according to a local hydrostatic p ressure gradient [22], [23]. The regional stress gradient is also a consideration, because the lateral pressure on a pipe varies accordingly over depth based on a lithostatic gradient.…”

Well Integrity for Natural Gas Storage in Depleted Reservoirs and Aquifers

“…Depth is an important factor to consider relative to wellbore integrity, because it is related to the likely potential pressure of the subsurface environment. Formation overburden pressure generally increases with depth according to a local hydrostatic pressure gradient [22], [23]. The regional stress gradient is also a consideration, because the lateral pressure on a pipe varies accordingly over depth based on a lithostatic gradient.…”

Enhancement of the rheological properties of bentonite mud using natural polymers

“…Temperature and pressure increase dramatically with the depth of the well. Oil and gas fields with temperatures and pressures above 230°C (440°F) and 160 MPa (23 000psi), respectively, have been reported [3,4]. Although there is not a universal definition, the term high pressure-high temperature (HPHT) is used by operators to indicate downhole temperatures in excess of 150°C (approximately 300°F) and pressures above 103 MPa (15000 psi) are referred to as ultra-or extreme-HPHT (xHHT or X-HPHT) wells [5].…”