海洋可控源电磁法次油气层探测模拟研究

Simulation study of secondary oil and gas reservoir detection using marine controlled source electromagnetic method

海洋可控源电磁(MCSEM)法在海洋油气开发中有着独特的作用,常用于油气层识别及辅助定位。海洋油气勘探中,主油气层附近往往存在次油气层,不易进行区分。在油气开采监测时,利用时移可控源电磁法检测次油气层,可以有效降低成本、提高勘探效率。首先,开展海洋可控源电磁法的二维正演模拟,对次油气层不同厚度、相较于主油气层的不同位置及不同距离、主油气层不同埋深的多种模型进行正演模拟,正演电磁响应表现出明显差异;然后,根据归一化振幅差异分析次油气层对电磁响应的影响;最后,采用OCCAM反演,对不同开采情况下的简单油气模型和复杂地质情况下的油气模型进行反演,结果表明,随着开采过程的进行,次油气层的响应逐渐清晰,为海洋油气开采监测提供可靠的参考数据。

Marine controlled source electromagnetic method plays a unique role in offshore oil and gas development,which is often employed to identify the oil and gas reservoir and assist in its location.In offshore oil and gas exploration,there are often secondary oil and gas reservoirs near the main oil and gas reservoir,which is hard to distinguish during exploration.In oil and gas exploitation monitoring,the adoption of a time‑lapse controlled source electromagnetic method to detect the existence of secondary oil and gas reservoirs can effectively reduce the cost and improve exploration efficiency.Firstly,the two‑dimensional forward simulation of the marine controlled source electromagnetic method is conducted to simulate various models with different thicknesses of the secondary oil and gas reservoir,location and distance compared to the main oil and gas reservoir,and different buried depths of the main oil and gas reservoir.The forward electromagnetic response shows obvious electromagnetic differences.Then,according to the difference in normalized amplitudes,the influence of the secondary oil and gas reservoir on the electromagnetic response is analyzed.Finally,OCCAM inversion is employed to invert simple oil and gas models under different production conditions and complex geological conditions.The results show that with the development of the production process,the response of the secondary oil and gas reservoir is increasingly clear,which provides reliable reference data for offshore oil and gas exploitation monitoring.