Experimental Research On The Characteristics Of Water And Oil Flowing Through The Water-sensitive And Low-permeability Reservoirs

The reservoirs of WN and KB are typical low permeability water-sensitive reservoirs.Because the low permeability reservoir has the characteristics of low permeability, lowporosity, complex pore types and poor connectivity. Low permeability reservoir flowcharacteristics is different from medium-high permeability reservoirs. Low permeabilitywater-sensitive reservoir has the typical charactristics of flow. Therefore，based on theunderstanding for fundamental geological characteristics of WN and KB reservoirs, throughindoor core flow experiments, oil and water flow characteristics and influencing factors aregiven a systematic experimental study. Through research the following key understandings areobtained in this paper:（1） WN reservoir’s main rock types are lithic arkose, feldspathic lithic sandstone andfeldspathic sandstone; rocks are mainly dominated by silt; the average value of the reservoirporosity distribution is9.7%; the average value of the distribution of permeability is2.54mD.KB reservoir’s main rock types are lithic arkose, feldspathic lithic sand stone and feldspathicsandstone; rocks are mainly dominated by medium sad, followed by giant sand, coarse sand,fine sand, silt, mud and gravel; the average value of the reservoir porosity distribution is10.3%; the average value of the distribution of permeability is10.8mD. The reservoirs of WNand KB are low－extra low permeability reservoirs;（2） The reservoirs of WN and KB are the middle-high water sensitivity reservoir; theaverage value of the reservoir water sensitivity damage rate are66.54%、57.2%; theillite/mixed layer and the chlorite/mixed layer, smectite are the major minerals which lead toreservoir water-sensitive; because of high water sensitivity of reservoir, water flow ability isrelatively poor, the formation water permeability is the gas permesbility of ten percent andtwenty percent;（3） The WN reservoir’s single-phase oil flow and the KB reservoir’s single-phase oilflow are obvious non-linear flow. The threshold pressure gradient of WN reservoir’ssingle-phase oil flow is relatively high, and it is in the range0.1844MPa/cm～1.4951MPa/cm，the average value is1.0204MPa/cm；the threshold pressure gradient of KB reservoir’s single-phase oil flow is relatively low, it is in the range0.00851MPa/cm～1.0387MPa/cm，the average is0.16858MPa/cm;（4） In this paper, through a variety of methods to calculate the threshold pressuregradient, the results show that, when calculating single-phase oil threshold pressure gradient,polynomial fitting method is most accurate; The WN reservoir’s single-phase oil and the KBreservoir’s single-phase oil threshold pressure gradient had a tendency to decrease with theincrease of gas logging permeability;（5） The WN reservoir’s anhydrous efficiency of water flooding is in the range6.9%～16.2%, the average value is10%, the final efficiency of water flooding is in the range35.5%～40.7%, the average value is38.1%; the KB reservoir’s anhydrous efficiency of water floodingis in the range4.5%～26.2%, the average value is12.1%, the final efficiency of water floodingis in the range32.2%～63.9%, the average value is46.6%; the injection water added intoanti-swelling agent can effectively inhibit the expansion of clay minerals in the reservoir rockand improve water flooding efficiency, increase range is15.34%to18.29%;（6） The WN and KB reservoirs oil-water two-phase relative permeability curves takeon typical oil-water relative permeability curves characteristic of hydrophilic low permeabilityreservoir, the aqueous permeability is low, the two-phase vadose zone is narrow.The results of the research lay a foundation for better developing the WN and KB lowpermeability reservoirs of water sensitivity and have some guiding significance for developingsimilar low permeability reservoir of water sensitivity too.