David M. Pritchard
Engineering at Fossil Hl Loop, Spring Branch, TX

8229671, Jul 24, 2012

Dec 10, 2009

12/635511

David M. Pritchard - Spring Branch TX, US
Kenneth J. Kotow - Sugar Land TX, US

G01V 1/40

702 6

A system and method for optimal placement of a riserless casing in a subsea drilling environment having the steps of: receiving input of pore pressure data for a well site; receiving input of fracture gradient for said well site; receiving input of the anticipated true vertical depth of said well site; integrating pore pressure data, fracture gradient data with said true vertical depth values; computing a pore pressure and fracture gradient verses true vertical depth graph; determining the true vertical depth at which the pore pressure begins to exceed the normal gradient of salt water; and determining the placement of a conductor casing string by corresponding the gradient true vertical depth to the true vertical depth of where the pore pressure beings to exceed the normal gradient of salt water. The method improves upon conventional placement of the riserless casing by optimizing the placement to achieve larger diameters in the wellbore, increased well depth, and mitigation of shallow hazards. Furthermore, the method of the present invention transforms readily available data to calculate optimal placement of a structural casing string to serve a dual purpose by providing not only structural integrity for the wellbore, but also ensuring leak-off integrity by taking advantage of the early growth of the fracture gradient of the natural subsea environment.