Llanos盆地W油田河道砂体识别与描述

Identification of Channel Sand in W Oilfield of Llanos Basin

南美洲Llanos盆地W油田的Carbonera组C5段内部C5^C小层发育水下分流河道,河道砂体与现低幅度构造匹配,形成了低幅度构造岩性油藏,但是C5^C层砂体厚度薄、横向变化大、非均质性强,其地震预测精度是该区石油勘探开发的瓶颈问题,直接影响钻探效果。为此,提出了＂五步法精细刻画河道砂体厚度＂的技术思路：首先,通过地层切片技术,刻画水下分流河道的展布趋势;其次,应用正演模拟技术建立储盖组合横向变化的地震调谐效应与地震响应特征;第三,应用叠后高分辨率处理技术进一步改善地震资料的分辨能力;第四,利用频谱成像技术定性预测了砂体的厚度变化趋势;最后,通过叠后约束稀疏脉冲反演技术定量描述C5^C砂体的厚度及顶面构造形态。该技术思路不仅落实了河道砂体分布,关键解决了砂体厚度定量预测问题,通过在C井区进行系统的应用,预测结果为探井开发井位部署提供更详实依据,得到了新钻井W-C4F的验证,由此打破前期认识的局限,发现了新油藏。

C5^C sand deposited in the Member C5 of the Carbonera formation is the main production layer of W oilfield in Llanos basin of Southern America.Low relief structure-lithologic reservoir came into being when the C5^C sand is located at favorable structure.Because of the thin thickness and the rapid variation of sand thickness,precision of reservoir prediction should be improved,otherwise,drilling effect will be affected directly. ＂Five-step＂ technical idea has been proposed to resolve this problem.First,strata slice analysis portrays the trend of sand distribution.Second,seismic forward modeling builds the knowledge of tuning effect and seismic response of the channel sand.Third,high resolution seismic process method is used to improve resolution of the seismic data.Fourth,spectrum decomposition is applied to study the tuning effect of C5^C sand of this area.At last,CSSI inversion method is adopted to characterize the target sand body and the surrounding rock quantitatively.All the study demonstrates that C5^C sand of number 2 channel is thicker than number 1 channel at the main part of channels.The prediction has been verified by the new well W-C4 F.As a result,preliminary study is updated,leading to the discovery of new reservoir.This idea has not only presented the sand body distribution in the channel,but also solved the problem of how to predict sand body thickness quantitatively.And the systematic application of it to C area provides a detailed reference to the arrangement of exploration well sites.