高能气体致裂技术在低渗砂岩型铀矿地浸开采中的应用

Application of High Energy Gas Fracturing in In-situ Leaching of Low-permeable Sandstone Uranium Deposit

鄂尔多斯盆地北部巴音青格利铀矿床赋存于直罗组下段下亚段中,矿体平均铀品位为0.057 1%,平均平米铀量为6.69 kg/m^(2);但其渗透系数仅为0.065 m/d,属典型低渗砂岩型铀矿。在常规地浸开采中,易出现抽注液量低、生产不经济等问题。为提高该矿床矿层的渗透性,选取注液能力较差的Z5井开展高能气体致裂增渗试验,同时使用微地震法在Z5井周围对高能气体压裂产生的裂缝发育情况进行监测。试验结果表明,致裂后Z5井注液量得到明显改善,平均注液量增加了126.34%,微地震监测事件点的纵向跨度在3.8~4.5 m,未破坏含矿含水层顶底板。高能气体致裂增渗技术能够使近井地带渗透能力得到改善,且方便实施,成本较低。

Bayinqinggeli uranium deposit in the northern of the Ordos Basin is hosted in the lower sub-member,lower member of Zhiluo Formation,with an average uranium grade of 0.0571%and an average uranium mass per square meter of 6.69 kg/m^(2),but its permeability coefficient is only 0.065 m/d,which is a typical low-permeable sandstone uranium deposit.For this deposit,the well Z5,which has poor injection capacity,is selected to carry out the high energy gas fracturing experiments.The uranium deposit aquifer of the well is located at 619~639 m,and the depth of the propellant is placed at 632.5~637.4 m,626.6~631.6 m,620.6~625.6 m.The amount of the propellant is 40 kg for each time.At the same time of fracturing,microseismic monitoring is carried out around well Z5.There are 59,61 and 49 events generated by the fracturing of three times,and the event profiles show that the fractures formed in the reservoir are trending at 46.8°NW,31.0°NW and 72.3°N,respectively.After fracturing,the injection volume of well Z5 is significantly improved,with an increasement of 126.34%.The high energy gas fracturing can improve the permeability of the near-well area.It is easy to implement and the cost is low.