基于地化热解录井和电阻率测井技术的江苏G油田水淹层实验响应特征和评价方法

Experimental response characteristics and evaluation method of water-flooded zones in Jiangsu G oilfield with geochemical pyrolysis and resistivity logging

江苏G油田某断块储层采用注淡水方式驱油,采用电阻率测井技术划分水淹层比较困难,而地化热解录井技术不受地层水矿化度变化影响,可以区分油层/弱水淹层与中水淹层、强水淹层。在模拟断块储层条件下,选用孔隙度相近的7块岩样作为一组,采用稳态法油水同驱制作不同产水率样品,测量样品地化热解参数和电阻率;选取岩样含油气总量(P_g)、原油轻重组分指数(PS)作为断块地化热解水淹敏感性参数,选取RFOC-RILD和RILD作为断块测井水淹敏感性参数,采用地化热解图版将油层/弱水淹层、中水淹层、强水淹层区分开,再利用电阻率图版将油层和弱水淹层区分开,建立录测结合水淹层评价图版,图版精度为83%,明显高于地化热解录井水淹层划分图版精度和测井水淹层划分图版精度。结果表明:随着产水率(F_w)升高,P_g、液态烃含量(S1)和热解烃含量(S2)降低,且P_g降低更明显;当注入水矿化度与原始水矿化度比为0.5时,0≤F_w≤10%样品的电阻率明显高于其他产水率范围样品的电阻率。随着水淹程度的增强,井壁取心样品PS呈现明显减小的趋势。地化热解录井与电阻率测井技术结合的水淹层评价方法可更好地实现G油田4级水淹级别的精细划分与解释。

Since oil in the reservoirs of Block X in Jiangsu G oilfield is displaced out with the method of fresh water injection,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.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-waterdisplacement in simulating the condition of reservoirs in block X,and then the geochemical pyrolysis parameters and resistivity of the samples are measured.Based on the analysis of the regulation of geochemical pyrolysis parameters and resistivity with the variation of water production rate,it shows that the geochemical pyrolysis parameters Pg,S1,S2 decrease with the increase of water production rate,and Pg shows more obvious variation.When the ratio of injected water salinity and original water salinity is equal to 0.5,the resistivity of the samples with the water production rate between 0% and 10%is much higher than that of the samples with the other water production rates.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 RFOC-RILD and RILD selected to be the sensitive resistivity parameters to divide water-flooded grades in block X.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.Finally,the chart of division for four waterflooded grades in G oilfield is established with combination of geochemical pyrolysis and resistivity log,and the accuracy of the chart is up to 83% and much higher than that of geochemical pyrolysis chart or resistivity chart.After the method proposed in the paper is applied to two 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.