方位伽马随钻测量技术在土耳其天然碱溶采对接井中的应用

Application of azimuthal gamma MWD technology in trona soultion mining with intersected well in Turkey

摘要:

随着土耳其贝帕扎里碱矿进入开采的中后期，大量钻井只能在矿区边缘地带布井施工。由于边缘处地层具有矿层薄、起伏大的特点，在进行水平对接井连通施工过程中，普通伽马随钻测量系统已无法达到碱层钻遇率的要求，诸多井组在水溶开采过程中出现不同程度的堵井，甚至报废。研制的方位伽马随钻测量系统，在现有MWD随钻系统的基础上，串入聚焦伽马探管，通过记录不同的窗口角度和伽马计数值，获取特定方向的自然伽马，由脉冲信号将方位伽马数据传输至地面接收机，通过对上伽马值和下伽马值的变化进行解析，可判断出钻孔是穿出矿层进入矿层顶板还是底板，能为定向工程师及时提供定向依据，重新找回矿层，保证钻遇率。在水平对接连通井水溶采矿应用过程中，除对已堵井进行修复外，新施工水平井直接采用方位伽马测量系统，能保证水平钻孔在碱层内钻进，可大大降低堵井事故的发生。

关键词:方位伽马;随钻测量;聚集伽马;上伽马值;下伽马值;地质导向;钻遇率;水平井;对接井;水溶开采;天然碱矿;土耳其

Abstract:

As the Beypazari Trona Mine in Turkey turns into its middle or late period of mining, plenty of well units situate at the edge of the mine area, where the trona bed is thin and its boundary is highly variable. While drilling horizontal intersected wells at this area with conventional gamma logging system, it is very difficult to ensure that the trajectory of the well to be remained at the trona layer, and the well sets were frequently blocked, or even abandoned during the process of solution mining. The newly developed azimuthal gamma LWD system, by adding focused gamma logging probe into conventional MWD instrument, is capable of recording gamma data of different window angles, to obtain gamma data of the specified orientation. The data is transferred from downhole to the receiver at the surface via mud pulse and processed. By comparing the gamma data at top and bottom direction, it can be determined that the drill bit is about to enter the ceiling or floor of the trona bed. This is an important information for the MWD engineer to adjust the tool face of directional instrument in time, to ensure the ratio of the trajectory within the trona bed. Besides its application in the workover the blocked well sets, the technology could also be applied directly into the newly constructed horizontal wells. With the utilization of this technology, the occurrence of well set blockage is dramatically decreased.

Key words:azimuthal gamma; measurement while drilling; focused gamma; top gamma value; bottom gamma value; geosteering; reservoirencountered ratio; horizontal well; intersected well; solution mining; trona mine; Turkey