Patent application 13752804 (US), filed 2013-01-29
Publication number: US20130192841A1
Title: DUAL GRADIENT MANAGED PRESSURE DRILLING
CPC codes: E21B  21/082
E21B   7/12
E21B  21/001
Office action: rejection, dated 2015-10-16
Rejection reasons: obviousness_103
indefiniteness_112
Prior art cited: ref_id: 20120234550
ref_type: patent
severity: obviousness
ref_id: 7367411
ref_type: patent
severity: obviousness
Final disposition: granted (2015-10-16)