风城陆相稠油油砂亲水性及润湿性机理研究

Wettability and hydrophilicity of Fengcheng terrestrial oil sand

风城陆相稠油油藏原油黏度高,通常采取挤液预处理储层改造结合SAGD方式开采。为了理解注入液和冷凝液在油藏中的运移规律,需要掌握该油砂的亲水和润湿机理。本文选取风城油砂样品,通过X射线衍射、环境扫描电镜、接触角和核磁共振系列实验,研究处于不同压差和酸碱度环境下的样品的亲水性与润湿性。研究发现风城油砂发育疏松结构,沥青作为砂粒彼此间的胶结物存在而不呈现"油包砂"的结构形式;风城油砂倾向于亲水,饱和盐水在岩心中以水膜和孔隙水两种形式存在;增大饱和压差或饱和盐水的酸碱度均会造成水膜变厚和孔隙水体积增加。综合分析可知,风城油砂亲水且水润湿,加大注入压差可更高效地将汽液注入地层,且添加化学用剂不会损害储层的可注性。

The terrestrial oil sand reservoirs in Fengcheng are characterized by their high viscosity and micro fracturing stimulation followed by SAGD has been commonly implemented.In order to understand how the injected fluid and the steam condensate infiltrate the reservoirs,the wetting and hydrophilic mechanisms of the oil sand must be interpreted.To this end,this study investigated oil sand sampled from Fengcheng for its wettability and hydrophilicity under various pressure gradients and acidities,through a series of laboratory studies including XRD,ESEM,contact angle and NMR tests.It was found that the oil sand develops a loosely packed microfabric,with bitumen forming the cementing agent between sand grains rather than wrapping the grains.The oil sand tends to be water-wet,with the wetting saline existing as both a water film and pore water in the matrix.Either increasing the pressure gradient or acidity/alkalinity is able to thicken the water film or increase the pore water amount.In summary,the Fengcheng oil sand is water wet and hydrophilic.An increase in the injection pressure gradient can bring in more steam or water into a reservoir,while adding chemical ingredients will not cause harm to the injectivity of the reservoir.