Pre-Drilling Prediction Techniques on the High-Temperature High-Pressure Hydrocarbon Reservoirs Offshore Hainan Island,China

Decreasing the risks and geohazards associated with drilling engineering in high-temperature high-pressure(HTHP) geologic settings begins with the implementation of pre-drilling prediction techniques(PPTs). To improve the accuracy of geopressure prediction in HTHP hydrocarbon reservoirs offshore Hainan Island, we made a comprehensive summary of current PPTs to identify existing problems and challenges by analyzing the global distribution of HTHP hydrocarbon reservoirs, the research status of PPTs, and the geologic setting and its HTHP formation mechanism. Our research results indicate that the HTHP formation mechanism in the study area is caused by multiple factors, including rapid loading, diapir intrusions, hydrocarbon generation, and the thermal expansion of pore fluids. Due to this multi-factor interaction, a cloud of HTHP hydrocarbon reservoirs has developed in the Ying-Qiong Basin, but only traditional PPTs have been implemented, based on the assumption of conditions that do not conform to the actual geologic environment, e.g., Bellotti's law and Eaton's law. In this paper, we focus on these issues, identify some challenges and solutions, and call for further PPT research to address the drawbacks of previous works and meet the challenges associated with the deepwater technology gap. In this way, we hope to contribute to the improved accuracy of geopressure prediction prior to drilling and provide support for future HTHP drilling offshore Hainan Island.

Evaluation and prediction of earth pressure balance shield performance in complex rock strata:A case study in Dalian,China

This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.

High-Temperature Overpressure Basin Reservoir and Pressure Prediction Model

Yinggehai Basin locates in the northern South China Sea. Since the Cainozoic Era, crust has several strong tension: the basin subsides quickly, the deposition is thick, and the crust is thin. In the central basin, formation pressure coefficient is up to 2.1;Yinggehai Basin is a fomous high-temperature overpressure basin.YinggehaiBasin’s in-depth, especially high-temperature overpressure stratum has numerous large-scale exploration goals. As a result of high-temperature overpressure basin’s perplexing geological conditions and geophysical analysis technical limitations, this field of gas exploration can’t be carried out effectively, which affects the process of gas exploration seriously. A pressure prediction model of the high-temperature overpressure basin in different structural positions is summed up by pressure forecast pattern research in recent years, which can be applied to target wells pre-drilling pressure prediction and post drilling pressure analysis of Yinggehai Basin. The model has small erroneous and high rate of accuracy. The Yinggehai Basin A well drilling is successful in 2010, and gas is discovered in high-temperature overpressure stratum, which proved that reservoir can be found in high-temperature overpressure stratum. It is a great theoretical breakthrough of reservoir knowledge.

Lateral earth pressure of granular backfills on retaining walls with expanded polystyrene geofoam inclusions under limited surcharge loading

Existing studies have focused on the behavior of the retaining wall equipped with expanded polystyrene(EPS)geofoam inclusions under semi-infinite surcharge loading rather than limited surcharge loading.In this paper,the failure mode and the earth pressure acting on the rigid retaining wall with EPS geofoam inclusions and granular backfills(henceforth referred to as EPS-wall),under limited surcharge loading are investigated through two-and three-dimensional model tests.The testing results show that different from the sliding of almost all the backfill in the EPS-wall under semi-infinite surcharge loading,only an approximately triangular backfill slides in the wall under limited surcharge loading.The distribution of the lateral earth pressure on the EPS-wall under limited surcharge loading is non-linear,and the distribution changes from the increase of the wall depth to the decrease with the increase of the limited surcharge loading.An approach based on the force equilibrium of a differential element is developed to predict the lateral earth pressure behind the EPS-wall subjected to limited surcharge loading,and its performance was fully validated by the three-dimensional model tests.

Prediction of Dynamic Wellbore Pressure in Gasified Fluid Drilling

The basis of designing gasified drilling is to understand the behavior of gas/liquid two-phase flow in the wellbore. The equations of mass and momentum conservation and equation of fluid flow in porous media were used to establish a dynamic model to predict wellbore pressure according to the study results of Ansari and Beggs-Brill on gas-liquid two-phase flow. The dynamic model was solved by the finite difference approach combined with the mechanistic steady state model. The mechanistic dynamic model was numerically implemented into a FORTRAN 90 computer program and could simulate the coupled flow of fluid in wellbore and reservoir. The dynamic model revealed the effects of wellhead back pressure and injection rate of gas/liquid on bottomhole pressure. The model was validated against full-scale experimental data, and its 5.0% of average relative error could satisfy the accuracy requirements in engineering design.

Research on Prediction Model for Erosion and Abrasion of Barrel Based on LSSVM

To predict the erosion and abrasion of high bore pressure tank gun barrel, the least square support vector machine (LSSVM) algorithm was used. Based on the gun firing test data, the prediction model for barrel's erosion and abrasion was established. It was adopted to predict the wear increment of gun barrel. The results show that the prediction values given by the model coincide with the measured data better, and the model can predict the barrel's wear accurately and rapidly.

Three-Dimensional Pressure Modeling of South China Sea in High Temperature High Pressure Field

Yingqiong basin is a proven hydrocarbon-rich basin in South China Sea. There are a number of large exploration prospects in high temperature and over-pressured formations, especially in Yacheng Block of Qiongdongnan basin and Dongfang District of Yinggehai Basin. Owing to good exploration situation, we have already achieved proven geological reserves over 1000 × 108 m3. In recent years, a few drilled HPHT wells have confirmed that pressure predicted by conventional method was wildly inaccurate. From the view of regional stress, the accuracy of the pressure prediction will be substantially improved. Accurate pressure prediction and three-dimensional pressure modeling which are based on three-dimensional lithology modeling are the cornerstone to achieve exploration breakthrough. In this paper, the use of the triple constraint trend lithology model broke through the traditional method of seismic lithology prediction only by means of impedance threshold value. Compared with actual data and prediction, it confirms that three-dimensional pressure modeling method is reasonable and effective, and has a wide prospect of application.

A coupled model of temperature and pressure based on hydration kinetics during well cementing in deep water

Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.

An artificial neural network visible mathematical model for real-time prediction of multiphase flowing bottom-hole pressure in wellbores

Accurate prediction of multiphase flowing bottom-hole pressure(FBHP)in wellbores is an important factor required for optimal tubing design and production optimization.Existing empirical correlations and mechanistic models provide inaccurate FBHP predictions when applied to real-time field datasets because they were developed with laboratory-dependent parameters.Most machine learning(ML)models for FBHP prediction are developed with real-time field data but presented as black-box models.In addition,these ML models cannot be reproduced by other users because the dataset used for training the machine learning algorithm is not open source.These make using the ML models on new datasets difficult.This study presents an artificial neural network(ANN)visible mathematical model for real-time multiphase FBHP prediction in wellbores.A total of 1001 normalized real-time field data points were first used in developing an ANN black-box model.The data points were randomly divided into three different sets;70%for training,15%for validation,and the remaining 15%for testing.Statistical analysis showed that using the Levenberg-Marquardt training optimization algorithm(trainlm),hyperbolic tangent activation function(tansig),and three hidden layers with 20,15 and 15 neurons in the first,second and third hidden layers respectively achieved the best performance.The trained ANN model was then translated into an ANN visible mathematical model by extracting the tuned weights and biases.Trend analysis shows that the new model produced the expected effects of physical attributes on FBHP.Furthermore,statistical and graphical error analysis results show that the new model outperformed existing empirical correlations,mechanistic models,and an ANN white-box model.Training of the ANN on a larger dataset containing new data points covering a wider range of each input parameter can broaden the applicability domain of the proposed ANN visible mathematical model.

Run by Run Control of Time-pressure Dispensing for Electronics Encapsulation

To alleviate the influence of gas compressibility on the process performance of time-pressure dispensing for electronics encapsulation,a predictive model is developed based on power-law fluid to estimate the encapsulant amount dispensed.Based on the simple and effective model,a run by run (RbR) supervisory control scheme is delivered to compensate the variation resulting from gas volume change in the syringe.Both simulation and experiment have shown that the dispensing consistency has been greatly improved with the model-based RbR control strategy developed in this paper.

Useful predictions ahead of large earthquakes and lessons learned for future progress

A significant basis for this article is the outcome of 4 multinational research projects which were carried out in South-West Iceland from 1988-2006,focusing on crustal processes that preceded two magnitude-6.6 earthquakes in June 2000.The seismic activity that preceded a magnitude 6.3 double-earthquake in the same seismic zone in 2008 is also significant,as well as other research work which helps to understand how observable crustal processes lead to earthquakes.A significant outcome is that it cannot be assumed that any two earthquakes have the same precursory processes.Therefore,statistical analysis of precursors of past earthquakes is of limited value for predicting future earthquakes.On the other hand,with highly sensitive seismic monitoring it is possible to observe the nucleation process for each specific large earthquake for long enough time for earth-realistic modeling of it and extrapolating towards the earthquake in time and space.In the Iceland crust,with its fluid-rock interactions,pre-earthquake activity on a scale of years is expected.This allows a long-term approach to prediction.We apply historical information and sensor-based data to find probable sources of earthquake nucleation.We monitor the nucleation process for a possibly impending earthquake at these sources,and then model the process to find its governing factors and extrapolate those in time and space,aiming towards finding hypocenter,fault-size,impact,and time of the impending earthquake.We refine our models by predicting frequent medium-sized earthquakes and compare the predictions with measurements.We predict how the possibly impending large earthquake would trigger earthquakes at other locations.Given the complexity of the crust,we must take all observed changes into account when developing models of pre-earthquake processes.The development of a continuously operating geo-watching system is discussed to link scientific evaluations to warnings that can be used by emergency authorities.

热室气动位置传感器反馈滞后补偿研究

热室辐照环境中的各类型射线会严重影响电子元件的服役寿命,因此目前多采用气动位置传感器来替代,其将感知及信号处理部分分别置于辐照环境和热室绿区来提高传感器的可靠性。由于气体的可压缩性,气动位置传感器存在信号反馈滞后现象。为了改善上述问题,分析了气动位置传感器的流量特性,建立了管道内流场数值模型并采用特征线法进行求解,构建了传感器压力响应预测模型,推导得到滞后量,并基于此提出了补偿策略。最后搭建了气动位置传感器响应检测平台,验证了预测模型及滞后补偿策略的有效性,结果表明:补偿后的位置相对预期值最大差值在0.5 mm以内,能够满足工程应用要求。

有界流场中潜艇水压场特性的预报方法和重要特征

潜艇水压场特性是信息化海战场的重要信息源。基于势流理论研究潜艇水压场特性的工程简化预报方法,构建基于兰金体线型的解析模型和基于回转体线型的数值模型,预估多种线型的潜艇水压场特性,并在验证性研究基础上,揭示潜艇线型、潜深等因素对潜艇水压场负压峰值、负压持续时间等重要特征的影响规律。研究结果表明:随着潜深增大,潜艇水压场负压区形状由单峰值的V形逐渐变为U形,甚至双峰值的W形,线型、潜深等因素对重要特征的影响逐渐增强;同一潜深下,随着航速增大,负压持续时间均呈现先突增、后缓降规律,且无论艇体胖瘦,其水压场重要特征在1倍艇长的横距外均已衰减,即该横距外水雷已难以捕捉其目标特性。

基于足底压力分布的下肢步态识别方法

良好的下肢步态感知性能有助于提升助力型外骨骼机器人的助力效果。本文以足底压力分布为研究对象,基于足底生物力学分析搭建一种可穿戴式足底压力分布采集装置,分别采集平地行走、平地慢跑和坡路行走3个步态的足底压力数据,并基于多元线性回归法构建的地面反作用力预测模型获取整体足压,提出了一种基于整体足压和卷积神经网络(CNN)分类算法进行下肢步态识别的方法,并与支持向量机(SVM)和反向传播(BP)神经网络进行了对比分析。试验结果表明:该方法对于3种步态的平均识别率达到98.3%,具有较高的准确性,验证了使用CNN分类算法对下肢不同步态识别的可行性与有效性。

经口气管插管患者口腔黏膜压力性损伤风险预测模型的构建及验证

目的构建并验证经口气管插管患者发生口腔黏膜压力性损伤的风险预测模型。方法纳入2022年12月至2023年7月浙江省某三级甲等医院ICU的400例经口气管插管患者为模型训练集,2023年8-10月的152例为模型外部验证集。采用logistic回归筛选口腔黏膜压力性损伤的预测变量。绘制受试者工作特征曲线下面积、校准曲线和临床决策曲线来评估预测模型的预测性能。采用Bootstrap法对模型进行内部验证。结果logistic回归结果显示,年龄、躁动-镇静程度量表评分、急性生理与慢性健康评分Ⅱ、血清白蛋白水平、气管插管操作者、气管导管固定方式和人工气道留置时间是口腔黏膜压力性损伤的影响因素(P<0.05)。训练集和验证集的受试者工作特征曲线下面积分别为0.913(95%CI:0.873~0.954)和0.956(95%CI:0.922~0.981);Hosmer-Lemeshow检验结果表明,模型预测值与实际值吻合较好,模型校准度较好(χ^(2)=1.702,P=0.427)。Bootstrap法重抽样结果显示,受试者工作特征曲线下面积为0.908(95%CI:0.852~1.105),灵敏度为94.9%,特异度为60.8%,准确率为83.7%。结论本研究构建的风险预测模型具有较好的区分度、校准度和临床应用价值,可为精准识别经口气管插管患者口腔黏膜压力性损伤高风险人群提供参考依据。

控压固井注入阶段流体密度和流变性分段预测方法

为解决控压固井注入阶段入井流体密度及流变性预测难的问题,设计了流体密度和流变性测量试验,基于试验结果优选了流变模式,建立了考虑不同流体性能差异的温压耦合模型,提出了流体密度和流变参数的分段预测方法。以川北地区X井为例进行了模拟计算,模拟结果表明:采用分段方法可将赫巴模式、四参数模式等多种流变模式作为优选对象,能更精确地描述流体的流变性;控压固井注入阶段采用常规计算方法,井口回压值偏低,大大增加了地层气侵风险,且不同方法预测的环空温度场相差不大;温度和压力的耦合作用对于流体密度和流变性及其变化规律的影响较大,也会对环空浆柱结构的设计及固井施工效果产生重要影响。研究结果为控压固井设计施工提供了理论依据。

基于肢体肌力及TcPO_(2)构建ICU病人压力性损伤预测模型

目的:采用肢体肌力及经皮氧分压(TcPO_(2))联合临床资料构建重症监护病房(ICU)病人压力性损伤的预测模型。方法:回顾性选取2021年4月—2023年1月我院ICU收治的429例病人作为研究对象。通过随机抽样按照7∶3比例将病人分为训练集(n=299)与测试集(n=130)。采用Logistic回归模型分析病人发生压力性损伤的影响因素,并借助随机森林算法构建随机森林模型。采用受试者工作特征(ROC)曲线下面积、灵敏度、特异度评价模型的预测效能。结果:训练集299例病人中71例发生压力性损伤,发生率为23.75%。多因素分析显示,合并糖尿病、急性生理与慢性健康状况(APACHE-Ⅱ)评分、Braden评分、TcPO_(2)、肢体肌力、机械通气、使用血管活性药是ICU病人发生压力性损伤的影响因素(P<0.05)。随机森林模型中预测因子重要性由高到低依次为TcPO_(2)、APACHE-Ⅱ评分、肌体肌力、Braden评分、机械通气、使用血管活性药物、合并糖尿病。测试集中,Logistic回归模型的ROC曲线下面积为0.871,灵敏度为84.5%,特异度为81.4%;随机森林模型的ROC曲线下面积为0.912,灵敏度为88.5%,特异度为84.2%。结论:ICU病人发生压力性损伤的影响因素为TcPO_(2)、APACHE-Ⅱ评分、肢体肌力、Braden评分、机械通气、使用血管活性药物、合并糖尿病,且随机森林模型对ICU病人压力性损伤风险的预测性能优于Logistic回归模型。

冻融循环后混凝土冲击劈拉强度预测模型

为预测混凝土材料冻融循环后冲击劈拉强度,本文对混凝土标准冻融试件和混凝土劈拉试件进行0、25、50、75、100次的冻融循环试验,通过动弹仪对混凝土标准冻融试件进行动弹性模量测试,采用电液伺服万能试验机和分离式霍普金森压杆系统分别在0.5和0.5×10^(6)、1.0×10^(6)、2.0×10^(6)kN/s的力加载速率下对劈拉试件进行劈拉试验,分析了冻融损伤以及力加载速率对混凝土冲击劈拉强度的影响。结果表明:随着冻融次数的增加,标准冻融试件的表观状况、质量、相对动弹性模量均不断劣化;当冻融次数一定时,随着力加载速率的提高,混凝土试件的冲击劈拉强度不断提升。在上述试验基础上,建立了冻融循环后混凝土冲击劈拉强度预测模型,该模型可为冻融循环后混凝土冲击劈拉强度的预测提供理论依据。

基于改进BERT模型的连续血压的预测方法研究

目前高血压已成为严重危害全球公共健康的重大问题。区别于传统的侵入式和袖带法的血压测量方式,为实时监测血压并助力早期诊断,本文专注于研究脉搏波波形与血压之间的内在关系,并提出了一种使用脉搏波的基于改进BERT(Bidirectional encoder representationns from transformers)模型的血压预测方法。方法首先应用巴特沃斯滤波器对原始脉搏波信号进行滤波预处理并周期性划分,然后结合深度学习技术,采用改进后的BERT模型,对划分后的脉搏波周期数据进行特征提取和分析。为验证本方法预测的有效性和准确性,采用MIMIC-Ⅲ数据库的数据进行实验。实验结果表明,本方法可以有效预测血压值,完全满足英国高血压学会的A类标准。通过深入研究脉搏波与血压的关系,本文改进BERT模型为高血压的预测与诊断提供了新的技术手段。