Casing Program Design Of High Pressure Gas Well

According to the analysis of the complicate geologic condition of high-pressure gas well and field practice statistical data, the conventional casing program can not satisfy the needs of high-pressure gas well because of the few programs and the small annular clearance between the casing and the formation. Not all of the complicate conditions can be completely indicated on the pressure curves, so the traditional design method that based on the pressure curves is no longer practicable.The seal-point depth calculating model is established and the surface casing depth is located considering the fracture extension; the casing design program begins at the seal-point and progress to both upside and downside;the unconventional casing programs are used to isolate the risky intervals and thus ensures the safety drilling and can satisfy the special qualification of high pressure gas well. Considering the gas tight effects, the casing string strength checking the internal pressure prior to the external pressure on the basis of safety factors appropriately selected thus is much different from the normal method in which the external pressure is the priority. The corrosion resisting materials and premium connections are used to meet the harsh requirements of high-pressure gas well. Then the strength and the tight qualification are totally satisfied. The visual program is completed that make the input and analysis of the data much convenient. Take Heba #1 well as an example and design the casing string using the conventional and seal-point method respectively. The method presented in this paper is much more approximate compared with the filed practice result thus can provide theoretical reference for the field operation.