Research On The Scheme Of Carbon Dioxide Huff And Puff Process In Wenliu Oilfield

Due to high temperature, high-salinity, high pressure, and low-viscosity geologiccharacteristic, the tertiary recovery technique in Zhongyun oil field has self-particularity.Now chemical flooding and MEOR technique can only be used in the reservoir, ofwhich temperature and salinity are below 90℃ and 10×104 mg/L respectively so thattheir applications are limited and can't be adapt the Zhongyun oil field harsh condition.More than one-third of OOIP in Zhongyun oil field is in low-permeability, especiallylow-permeability reservoirs, of which permeability is less than 50× 10-3μm2. To thesereservoirs the injecting water technique doesn't meet the production demand and thenature energy is mainly available for production so that efficiency of production is lowand the efficiency is only from 15% to 20%. How to develop the low-permeabilitydeep reservoirs is a problem to field and a chance and a challenge for increasing andstabling reserves. It is important for increasing and stabling reserves for field to enhancethe development efficiency of these reserves. At present there are 700 wells that are ofnatural energy or water injection, the total OOIP is about 60 million tons. This lowrecovery ratio, potential wells are suitable for huff-puff working. After many yearresearch and expert evaluation, carbon dioxide huff-puff and miscible flooding is thepossible way for zhongyuan oil field. With the characteristics of low invest and fasteffect, the technology shows some suitability to the reservoirs. So it is very necessary tobegin this work for future flooding.With the referral to the well choosing conditions aboard and reservoircharacteristics, four different wells in Wenliu were chosen for lab test and reservoirnumerical imitation research in order to study the production mechanism and effect ofcarbon dioxide huff-puff for future application.The gas-injection expansion tests and multiple-degas tests of crude oils showed thefollowing huff-puff mechanism ----with the increasing of the carbon dioxide mole percent, the injection pressure goes up, the oil/gas ratio changes greatly, especially thedissolved oil/gas ratio goes up greatly, the reservoir oil volume expands greatly, but thedensity and the viscosity decrease greatly, all these changes are very helpful for theproduction.The optimization of injection and recovery design resulting from the CMGcomposition model showed the optimization of the parameters of the carbon dioxideinjection amount, the injection speed, the time of shutoff, and the production speed isvital for a better production.