Three-dimensional deformation over Shuguang oilfield in Liaohe River Delta, China, from multi-track InSAR and its impacts on flood inundation

Land subsidence has a great impact on coastal plains near sea level, leading to permanent inundation. The Shuguang oilfield, located in Liaohe River Delta (LRD), northeastern China, is one of the most significant subsidence areas as a direct consequence of oil production. We studied the production-induced deformation in the LRD region by Sentinel-1 radar images. Images from two ascending and two descending tracks are processed by an Interferometric Synthetic Aperture Radar (InSAR) time series analysis over the 2017 to 2021 period, providing deformation rate maps and time series in the radar line-of-sight (LOS) direction.

Previous researches carried out in this area assumed the oil production-induced deformation corresponds only to vertical deformation. Here, we proposed a method to retrieve the three-dimensional (3D) displacement field over the oilfield. We retrieved the vertical and east-west deformation components by combining the multiple InSAR geometries LOS observations and retrieved the north-south component based on the assumption of a physical relationship between the horizontal and vertical displacement.

The derived 3D displacement fields over Shuguang oilfield exhibit a circular subsidence bowl with a maximum subsiding rate reaching 212 mm/year, accompanied by a centripetal pattern of horizontal displacements with maximum rates up to 50-60 mm/year moving towards the subsidence center. The retrieved-3D displacements are in good agreement with predictions from the geomechanical modeling by assuming a disk-shaped reservoir subject to a uniform reduction in pore fluid pressure. Finally, we show the importance of knowing both the vertical and horizontal displacement in characterizing the lateral boundary of the subsurface reservoir.

The Liaohe River Delta region is often affected by heavy rainfall and storm surge in flood season, and flood disasters occur frequently in this low-lying coastal area. This deltaic region is vulnerable to floods not only from the extreme heavy rainfall, but also the land subsidence related to oil production. By spatial overlay analysis of the land subsidence distribution and the inundation extent of a flood event in August 2022, we reveal the impacts of land subsidence on flood inundation in this region. Our findings provide scientific support for oil production-related subsidence control and flood planning and designing in this deltaic region.

土地沉降对海平面附近的沿海平原有着重大影响，导致永久性淹没。位于中国东北辽河三角洲（LRD）的曙光油田是油气生产直接引起的最重要沉降区之一。我们通过使用Sentinel-1雷达影像研究了辽河三角洲区域的生产诱发变形。来自两个上行轨道和两个下行轨道的影像，经过2017到2021年期间的干涉合成孔径雷达（InSAR）时间序列分析处理，提供了雷达视线（LOS）方向的变形速率图和时间序列。

以往在该区域的研究假设油气生产引起的变形仅对应垂直变形。在本研究中，我们提出了一种方法，用于提取油田的三维（3D）位移场。通过结合多几何InSAR视线观测，我们获取了垂直和东西方向的变形分量，并基于水平位移和垂直位移之间的物理关系假设，估算了南北方向的变形分量。

提取的曙光油田三维位移场展示了一个圆形沉降盆地，最大沉降速率达212毫米/年，同时伴随有一个向沉降中心指向的水平方向变形模式，最大水平方向位移速率达50-60毫米/年。提取的三维位移与地质力学建模的预测结果良好吻合，假设储层为盘状，经历孔隙流体压力的均匀降低。最后，我们展示了了解垂直和水平方向位移在表征地下储层侧边界方面的重要性。

辽河三角洲区域常常受到暴雨和风暴潮的影响，洪水季节经常发生洪水灾害。该三角洲地区不仅受到极端暴雨的洪水影响，也受到与石油生产相关的土地沉降的影响。通过空间叠加分析土地沉降分布和2022年8月一次洪水事件的淹没范围，我们揭示了土地沉降对该地区洪水淹没的影响。我们的研究结果为石油生产相关的沉降控制以及该三角洲地区的洪水规划和设计提供了科学支持。