NEW INSIGHTS INTO INTERCALATION AND INTERLAYER MODELING INCORPORATING OBSERVATIONS FROM OUTCROP ANALOG

Carbonate cemented intercalations or interlayers, are well developed in Tarim Basin. Conventional modeling method cannot effectively characterize their horizontal distribution. This study established relationship between thickness and length of the interlayers by observations from outcrop to better control the spacial distribution of them.

Luxemburg sandstone in Paris Basin is extensively exposed in outcrops, which is similar with the carboniferous strata of study area in terms of sedimentary environment, structural background, and petrology characteristics such as constituent grains and cements. Based on statistics of 344 outcrop observation data, the relationship of thickness and length of cemented layers in the direction perpendicular to the provenance is: T = 4/30 * lg(l) + 11/60 (Equation A).

In the cemented layers modeling process, the parameters were controlled by an "intercalation indicator" log (sampling interval at 0.125 m) of each well with value 0,1, and 1 indicates development. Statistics reveal the cemented layer with length in the direction perpendicular to the provenance greater than 40 m would become intercalation, or it is interlayer. "Intercalation indicator" log (values 0,1) is a thickness indicator with seven values (0-6). "6" represents the situation when the value of "1" consecutively occurs more than 5 times, and then all "1" are replaced by "5" automatically. Whereas "5-1" represents the value of "1" consecutively occurs from 5 to 1 times. "0" represents no intercalation as well. According to the formula mentioned above, the thickness cutoff is 0.4 m : the cemented layers that are less than 0.4 m in thickness, i.e. with log value of 1-4, are defined as interlayer facies; while the cemented layers that are greater than 0.4m, i.e. with log value of 5-6 are defined as intercalation facies. The corresponding length of each facies could be calculated by Equation A and is set as the horizontal range of each facies respectively. The cemented layer model was then built based on the horizontal range with the algorithm of Sequential Gaussian Simulation. Comparing to conventional method, the modeling strategy proposed in this study effectively controls the horizontal distribution of the cemented layer, as well as takes account of various barrier effects of cemented layers with different ranges.