井中重力测量及其在我国石油勘探中的应用前景

Borehole gravity measurement and its application prospects in China's petroleum exploration

井中重力测量是近期发展起来的一种地球物理方法.其特点是在井中一系列测点上测量不同深度的重力值。影响仪器测量的因素有,①自由空气效应.它使重力值随测井深度增大而增大;②中间层(布格层)效应,即横向密度均匀分布的水平层状介质引起的引力影响;③异常密度分布的重力效应,它表明地壳中未构成水平均匀密度层的其它质量(异常质量)所引起的重力影响,即井中布格重力异常;④地表或海底地形的重力效应;⑤与井眼有关的例如井径、套管、泥浆等引起的重力效应。经过对上述影响因素的校正.便可得到反映井下异常体分布的垂向重力异常曲线。井中重力测量具有受干扰因素少,精度高的优点,它在油气勘探中具有广阔的应用前景。

Borehole gravity measurement is a new geophysical method. It measures gravity values at different depth points in borehole. The gravity measurement values can be influenced by these factors : ·free air effect.which makes gravity values raise with the increase of depth; ·intermediate layer (Bouguer layer) effect, namely the attraction effect that results from the horizontal layered medium whose density is laterally uniform; ·gravity effect of abnormal density body,or borehole Bouguer gravity anomaly, caused by abnormal mass body which is in dependent of horizontal uniform density layers in crust; ·gravity effect due to surface landform or ocean bottom landform; ·gravity effect relating to borehole environment such as borehole diameter.casing,mud and so on. The vertical gravity abnormal trace which reflects the distribution of borehole abnormal bodies can be obtained by removing the above influence factors. Because of less disturbance and higher accuracy borehole gravity measurement will find its wide application in hydrocarbon exploration.