Based on the study of the gas reserve scale and oil-gas distribution for ordinary heavy oil reservoir with gas cap of Cao 31 fault block in Lean oilfield, using reservoir engineering and numerical simulation, optimizing study on development technical limits for oil reservoir with small gas cap including production method, well pattern, waterflooding time is carried out.

Nine sorts of well patterns for thermal recovery are designed for three types of super heavy oil reservoirs in Shengli petroliferous province.

Optimal well pattern and optimum fractures are the important link of development program,they also play a decisive part in expanding recoverable reserves,recovery factor and production of natural gas.

Taking one sandstone reservoir as an example, the effect of well completion ways on critical pressure differential and well productivity in sandstone reservoir has been studied by triaxial elasto-plasticity finite element model for sand prediction.

During the polymer flooding in unconsolidated sandstone reservoirs,reduction of polymer solution viscosity might be caused because of unreasonable selection of sand control completion method,and consequently polymer flooding effect would be affected.

On the basis of researching the empirical formulas of productivity calculation of the oil & gas well completion both in China and broad, and several common completion methods in shallow gas pool of east Sichuan gas field, the mathematical model for predicting completion productivity has been established.

Based on the Grey Theory, a new method to choosing the optimal completion method was proposed, which considered the initial productivity, the accumulative productivity, the NPV, the expense, the dynamic invest payback period.