Experimental Response Characteristics And Interpretation Method Of Geochemical Pyrolysis For Water-Flooded Zones In Jiangsu Oilfield

Since oil in the reservoirs of Jiangsu oilfield is displaced out with the method of water injection and complex variation of formation water salinity is made, it’s difficult to distinguish high, middle, weak water-flooded zones with resistivity logs. However, the geochemical pyrolysis mud logging technology can distinguish oil zones or weak water-flooded zones, middle water-flooded zones and high water-flooded zones very well as it is not affected by variation of formation water salinity. Therefore, interpretation method of geochemical pyrolysis for water-flooded zones is studied further to inhence interpretation correctness of water-flooded zones, and it’s more accurate to distinguish the four water-flooded grades by the combination of advantages of geochemical pyrolysis and resistivity logging in the evaluation of water-flooded zones.In the paper seven samples with similar porosity are chosen as a group, and samples with different water production rate are made by steady state method of oil-water displacement in simulating the condition of reservoirs in Jiangsu oilfield, and then the geochemical pyrolysis parameters of the samples are measured. Based on the analysis of the regulation of geochemical pyrolysis parameters with the variation of water production rate, it shows that the geochemical pyrolysis parameters P_g, S₁, S₂ decrease with the increase of water production rate, and Pg shows more obvious variation. The reduction coefficient of gross hydrocarbon quantity（PI） is proposed, and it is proved theoretically that PI can eliminate the influence of porosity variation on gross hydrocarbon quantity. After analyzing the variation of the geochemical pyrolysis parameters PS of sidewall cores with water production rate, it shows PS has a downward trend with the increase of water-flooded degree. Based on the results mentioned above, Pg and PS are selected to be the sensitive geochemical pyrolysis parameters, and the water-flooded geochemical pyrolysis chart is established. RFOC-RILD and RILD are selected to be the sensitive resistivity parameters, and the water-flooded resistivity chart is established with them. First, the water-flooded geochemical pyrolysis chart is used to divide oil zones or weak water-flooded zones, middle water-flooded zones, and high water-flooded zones. Second, oil zones can be distinguished from weak water-flooded zones by the water-flooded resistivity chart. At last, the chart of division for four water-flooded grades is established with combination of geochemical pyrolysis and resistivity log, and the accuracy of the chart is higher than that of geochemical pyrolysis chart or resistivity chart. After the method proposed in the paper is applied to well data, the result shows that the method of evaluation of water-flooded zones can distinguish the four water-flooded grades better with the combination of geochemical pyrolysis and resistivity log in Jiangsu oil field.