Recovery Mechanism Research For Nature Gas Buff-Puff In Deep Heavy Oil Reservoir

Heavy oil resources of China are ultradominant.Now, thermal recovery methods are the main development technique, which are adapt to lighter buried depth reservoirs. For deep ones, heat loss is great and economic benefit is poor, so many ones can not be developed effectively. Nature gas buffing and puffing has obvious advantages, such as viscosity reducing and per well production raising effects, which is a new technique in deep heavy oil exploitation and has a good popular and applied foreground.This paper bases on gas injection enhanced recovery and heavy oil CO₂ huff and puff research, developes nature gas buff-puff physical simulation devices, carries out heavy oil/nature gas equilibrium and non-equilibrium state law research and experimental study of nature gas buff-puff physical simulation, summarizes nature gas buff-puff general laws, proposes this idea that the main increase production mechanism of nature gas buff-puff is that artifical motivate can form foamy oil. Then, it establishs partition zone fluid flow model of nature gas buff-puff process and analyses variation law in pressure and fluid in nature gas buff-puff process. Optimization of nature gas buff-puff system is researched by the numerical simulation technology, effect of field experiment is evaluated. So it offers significant theory and guide basis for nature gas buff-puff prevalence and apply.By intensive research, we have obtain these outcomes:1、Interactive mechanism and crude oil property change on Nature gas and heavy oil are obtained. By the way of experiment, we verify that PVT property and non-interactive phase characteristic both equilibrium, Except conventional dissolve viscosity break mechanism, the first mechanism is present pseudo bubble point after injecting gas in heavy oil, and upper viscous drag of heavy oil makes lots of minute bubbles break away from liquid phase, moving along with heavy oil and making foamy oil stream, thus forming foamy oil decentralized viscosity break. which provide development base for nature gas buff-puff.2、Nature gas buff-puff physical simulation devices is builder. According to feature of deep heavy oil exploitation of nature gas buff-puff, we develop the nature gas buff-puff physical simulation devices. This one is multi-purpose, can simulate CO₂,N₂, nature gas buff-puff, water alternate gas（WAG） and can monitor pressure of various position, which provide shop experiment demonstration tool for nature gas buff-puff.3、With the help of devices developed, production feature of nature gas buff-puff is researched. During the nature gas buff-puff process, it is divided into super saturation zone、pseudo saturation zone、saturation zone and under saturation zone from gas injection well bottom to distal strata formation. Pseudo saturation zone is the import production phase for oil well.4、By physical simulation, we simulate various production mode of nature gas buff-puff. Production law on various buff-puff mode and production feature of nature gas buff-puff are sighted generally, The best process of nature gas buff-puff exploitation is maintaining reservoir pressure recovery, which provide field trial for nature gas buff-puff.5、With respect to super-high viscosity of Tuha heavy oil, we optimize routine of work of nature gas buff-puff and obtain effect of production cycle, cyclic gas injection,injection rate, shut-in time to production performance. Then field experiment is carried out and good and positive effect is got.