稠油油藏火驱前后储集层变化定量表征——以辽河油田高3-6-18井为例

火驱是稠油油藏继蒸汽吞吐后提高采收率的技术之一。储集层是决定火驱开发效果的根本因素,而温度是影响火驱储集层变化的主要因素。以辽河油田高3-6-18井为例,通过模拟实验,得到火驱过程中不同阶段的样品,分析了火驱前后储集层的变化,建立了研究区火驱过程中储集层变化模式。研究表明：结焦带的储集层物性较差,Fe（OH）₃沉淀物、CaCO₃沉淀物和沥青质沉积堵塞孔喉,长石向黏土矿物转化,同时生成大量的硅质胶结物,破坏了粒间孔与粒内溶孔,使孔隙度和渗透率降低,物性变差;燃烧带和已燃带的储集层物性较好,Fe（OH）₃和CaCO₃沉淀物分解、沥青质沉积的裂解,使孔喉增大,黏土矿物的烧结作用使高岭石向蒙脱石、伊利石转化,同时存在蒙脱石向伊利石的转化,使以黏土矿物为主的粒间填隙物发生不同程度的体积收缩,颗粒和填隙物之间产生裂缝,并随温度升高,裂缝会明显加宽,孔喉增大且连通性变好,孔隙度与渗透率升高。

Quantitative Characterization of Reservoir Changes Before and After Fire Flooding in Heavy Oil Reservoirs: A Case Study of Well Gao 3-6-18 in Liaohe Oilfield

Fire flooding is one of the techniques for enhancing oil recovery in heavy oil reservoirs after steam stimulation. Reservoir is the fundamental factor influencing the effect of fire flooding, while temperature is the main factor affecting the changes of reservoirs during fire flooding. Taking the Well Gao 3-6-18 in Liaohe oilfield as an example, based on the physical simulation experiments and the samples obtained from different fire flooding stages, the change mechanism of reservoirs before and after fire flooding was analyzed, and the corresponding reservoir change patterns were established. The study shows that the physical properties of the reservoir in the coking zone are poor. The precipitates of Fe(OH)₃ and CaCO₃ and asphaltene sediments make the pore throats blocked. The clayization of the feldspar, accompanied with the forming of a large amount of siliceous cements, destroying the intergranular pores and the intragranular dissolved pores and leading the reduction of porosity and permeability. The reservoirs in the combustion zone and burned zone have better physical properties, in which the decomposition of precipitates of Fe(OH)₃ and CaCO₃ and the cracking of asphaltene sediments can enlarge the pore throats, the sintering of clay minerals makes kaolinite transform into montmorillonite and illite, along with the transformation of montmorillonite to illite, resulting in the volume contraction of intergranular interstitial materials dominated by clay minerals, and finally cracks occur between the particles and the interstitial materials. With the increase of temperature, the cracks become wider, the pore throats become bigger and the connectivity becomes better, then the reservoir porosity and permeability increase as well.