钻井液侵入海洋含水合物地层的一维数值模拟研究

本文以墨西哥湾水合物区域为背景，利用数值模拟方法研究了过平衡钻井条件下，当钻井液温度高于地层中水合物稳定温度时，水基钻井液侵入海洋含水合物地层的动态过程及其一般性规律．与侵入常规油气地层相比，耦合水合物分解和再形成是钻井液侵人海洋含水合物地层的主要特征．模拟结果表明，钻井液密度、温度和盐度都对侵入过程有影响．在一定条件下，钻井液密度越大，温度和含盐量越高，则钻井液侵入程度越深，热量传递越远，水合物分解程度越大．分解的水气在合适条件下又会重新形成水合物，影响了钻井液进一步侵入．而重新形成的水合物的饱和度甚至可能高于原位水合物饱和度，在井周形成一个“高饱水合物”环带．这一现象归因于钻井液侵入的驱替推挤、水合物分解的吸热以及地层传热的滞后等因素共同作用．在地层物性一定的条件下，高饱水合物环带的出现与否主要受钻井液温度和盐度控制．水合物分解以及高饱水合物环带的出现对井壁稳定和电阻率测井解释有很大影响．因此，为维护井壁稳定、确保测井准确和减少水合物储层伤害，就必须对钻井液密度、温度和滤失量进行严格控制，防止地层中的水合物大量分解．最好采用控制压力钻井（MPD）和深侧向测井方式，同时尽量选用低矿化度的含水合物动力学抑制剂的钻井液体系，采取低温快速循环方式

基于常规测井方法估算原位水合物储集层力学参数

以南海神狐SH7井和阿拉斯加冻土区Mount Elbert井为例,基于常规油气储集层利用测井数据估算地层力学参数的方法,估算海洋区和冻土区水合物储集层力学参数,并与其他研究者的测试或计算结果进行对比。算例分析结果表明：根据常规油气储集层力学参数与声波波速间的关系式,利用测井结果可以估算海洋区水合物储集层的内聚力、内摩擦角、抗拉强度和抗剪强度,但海洋区水合物储集层泥质含量、冻土区水合物地层内摩擦角、海洋区和冻土区水合物地层杨氏模量及体积模量的估算结果误差较大;建立适用于水合物储集层的力学参数与声波波速或水合物饱和度间的关系式,并通过测井方法获取声波波速或水合物饱和度数据,可以更准确地估算原位水合物储集层力学参数

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies