海塔油田螺旋井眼的形成原因与预防措施

海塔油田所钻井中螺旋井眼比例大,造成对比分层不准、油水层识别困难,给地质分层解释带来不利影响。为解决该问题,分析了螺旋井眼的产生机理;结合海塔油田地质特征和钻井施工现状,从地质因素和工程因素2方面研究了海塔油田产生螺旋井眼的主要成因;对钻井工具、钻头、钻井参数和钻井施工措施等进行了分析总结,形成了海塔油田预防螺旋井眼的技术措施。该技术措施的主要内容是:采用直螺杆钻进,弯螺杆纠斜,使用钟摆钻具组合以增大钻具组合刚度,稳定钻具的工作状态;采用保径钻头,降低钻头侧向切削井壁;控制钻压和钻速,及时修正井壁,保证井壁光滑。现场试验表明,该技术措施可大大降低螺旋井眼的发生概率,保证海塔油田地质分层和油水层识别准确及测井工作的顺利进行。      

螺旋井眼的产生、危害和防止

井眼质量一般与井眼的光滑程度或扭曲有关，由于地层和钻具相互作用的复杂性，随着进尺的增加，曲率和挠率不断变化，因此，除非采取特剐措施，实际钻出的井眼基本是螺旋井眼，它的形成造成了滑动摩擦力增大、钻压传递困难、滑动钻进机械钻速低、下套管阻力大、测井仪器下放困难、钻具失效快、井眼清洁困难、倒划眼切削新岩石等问题。为了减少建井费用、提高井眼质量，必须对螺旋井眼的产生、危害及其防治进行研究。介绍了这方面研究新进展、并探讨了螺旋井眼产生的机理、危害、预防措施和未来的若干研究问题。     

侧钻水平井钻柱与井眼的相容性研究

套管内侧钻水平井由于井眼曲率比较大,钻具与井眼环空间隙较小,要求下部钻具不仅有较高的造斜率,而且环空的间隙尽量大,以提高钻井液的携岩能力,需要在套管内下人弯螺杆钻具组合,由于弯螺杆钻具初始弯曲较大,而套管内径较小,因此,钻柱与井眼的相容性是侧钻水平井钻井的关键技术之一。在实际的侧钻水平井钻井作业中,为了避免和预防因为下部钻具组合与井眼不相容而造成的下钻遇阻甚至卡钻事故的发生,需要研究钻具与井眼之间的相容性,以指导施工中钻具组合的正确设计、评价以及合理使用各种钻具组合、减少阻卡的可能性。为此,讨论了侧钻水平井钻柱与井眼之间相容性的主要影响因素及变化规律,并针对大港油田侧钻水平井的实际情况提出了改善钻柱与井眼相容性的方法和措施。     

下部钻具刚度与井眼相容性分析

本文讨论了水平井钻井作业中螺杆钻具与井眼的相容性问题和带稳定器旋转钻下部钻具组合与井眼相容性问题，并在文章最后给出了五条结论。     

定向井井眼轨迹的连续控制

目前,大多数定向井采用常规的钻井工艺技术进行井眼轨迹的控制(即非连续控制),一口井要改变钻具结构多次,而每次改变钻具结构需起下钻方能实现。导向钻井系统可实现井眼轨迹的连续控制,靠一套多功能下部钻具组合一次下井,配合长寿命的优质钻头和随钻测斜仪导向,在井下长时间运转,不用起下钻就能准确、连续、迅速、经济地完成定向井多种井段的作业。该技术的推广应用,将会取得很大的经济效益。     

影响井眼轨迹的诸种因素

影响井眼轨迹的主要因素,可以概括为钻具下部组合、钻井操作参数、已钻井眼几何及待钻地层特性等几类。本文以钻具下部组合权余法分析及钻头与地层相互作用研究为基础,分别讨论了这些因素对井眼轨迹的影响规律,给出了一些重要结论,可供钻井技术人员参考。     

长井段大尺寸井眼钻具疲劳失效分析模型建立与应用

塔河油田开发井均为深井,二开444.5 mm钻头须钻至3 000 m左右,平均钻速8 m/h左右,钻井过程中易出现钻具失效事故,导致该油田万米进尺故障率居高不下。为了有效缩短钻井周期、安全实施快速钻进,分析了长井段大尺寸井眼钻具失效原因,在刚杆模型的基础上,建立了长井段大尺寸井眼钻具疲劳失效分析模型。塔河油田TH1井实例分析表明:扶正器的存在是导致钻具疲劳失效的主要因素,钻井参数不合理也易导致钻具的疲劳损坏;实施钻具组合和钻井参数的优化设计能有效降低钻具疲劳失效的风险。本文研究成果可为长井段大尺寸井眼的钻具组合和钻井参数的优化设计提供技术支持。     

随钻扩眼技术在渤海某油田的应用

随钻扩眼技术采用随钻扩眼工具配合常规钻头钻具组合,在正常钻进的同时扩大原井眼,不仅减少了起下钻时间,提高了机械钻速,同时也降低了卡钻风险,已逐渐成为一种应对塑性蠕变复杂地层、优化井身结构、提高油气井建井质量、提高钻井速度、降低钻井作业成本的钻井新技术。     

侧钻水平井井眼轨迹控制技术

井眼轨迹控制是侧盐水平井钻井施工的关键技术，是决定侧盐水平井钻井成败、钻井费用及生产能力的重要因素。与常规水平井相比，侧盐水平井由于井眼曲率大、钻具刚度低、中靶要求高，因此要求井眼轨迹控制不仅要有较高的控制精度和预测准确度，还应对油层垂深误差、工具造斜率误差、井底参数预测误差具有较强的适应能力。本文介绍了φ139．7mm套管开窗侧钻水平井井眼轨迹设计、钻具组合设计与井眼轨迹控制施工工艺，包括初始造斜侧钻、井眼轨迹测量、井眼轨迹控制软件及造斜段、水平段轨迹控制方案。     

导眼与扩眼组合钻进模式在定向井轨迹控制中的应用

定向井由于受诸多因素影响,其实钻轨迹有时并不沿着设计轨道钻进,给钻井施工带来很大挑战。不考虑地层特性、钻井参数、井眼轨迹等影响因素,采用简单实用且可满足工程要求的公式,计算和分析了单弯单稳螺杆钻具组合的理论几何造斜率。研究了井眼及钻具尺寸对造斜率的影响,发现相同条件下小井眼比大井眼更易获得高造斜率。由此提出在造斜率要求较高的井段,可先钻一个小尺寸导眼,再扩眼到设计尺寸的组合钻进模式。以X井为例,证实了在轨迹控制困难的定向井中,采用该组合模式后,满足工程要求且降低作业成本,缩短钻井周期。研究结果为井身结构设计和定向井轨迹控制提供了理论指导和借鉴。     

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井眼质量一般和井眼的光滑程度及扭曲有关，由于钻具和地层相互作用的复杂性，随着进尺的增加，井眼曲率和挠率不断变化，在井壁的限制和钻进惯性的影响下，实际钻出的井眼基本都是螺旋井眼，它的形成造成了轴向和周向摩擦力增大、钻压传递困难、钻进机械钻速低、下套管阻力大、测井仪器下放困难、钻具失效快、井眼清洁困难、倒划眼切削新岩石等问题。目前衡量井眼质量很少提到螺旋的问题，对于其产生的机理和防治措施方面所做工作甚少。为了减少建井费用、提高井眼质量，研究螺旋井眼的产生、危害及其防治提上了日程。章介绍了国外这方面研究新进展，着重并探讨了螺旋井眼产生的危害、机理、预防思路。     

Control of hydrocarbon accumulation by Lower Paleozoic cap rocks in the Tazhong Low Rise, Central Uplift, Tarim Basin, West China

Despite the absence of regional cap rocks in the Lower Paleozoic for the entire Tazhong Low Rise,several sets of effective local cap rocks are well preserved on the Northern Slope.Of these the best is the Ordovician mudstone of the Sangtamu Formation; the second is the Silurian Red Mudstone Member of the Tatairtag Formation and the marl of the Ordovician Lianglitag Formation; and the third is the gray mudstone of the Silurian Kepingtag Formation.The dense limestone of the Ordovician Yingshan Formation and the gypsum of the Middle Cambrian have shown initial sealing capacity.These effective cap rocks are closely related to the distribution of Lower Palaeozoic hydrocarbons in the Tazhong Low Rise.With well-preserved Sangtamu Formation mudstone and its location close to migration pathways,rich Lower Paleozoic hydrocarbon accumulation can be found on the Northem Slope.Vertically,most of the reserves are distributed below the Sangtamu Formation mudstone; areally,hydrocarbons are mainly found in the areas with well-developed Sangtamu Formation mudstone and Lianglitag Formation marl.Burial history and hydrocarbon charging history show that the evolution of Lower Palaeozoic cap rocks controlled the accumulation of hydrocarbon in the Tazhong Low Rise.Take the Red Mudstone Member of the Tatairtag Formation and Sangtamu Formation mudstone for examples：1） In the hydrocarbon charging time of the Late Caledonian-Early Hercynian,with top surfaces at burial depths of over 1,100 m,the cap rocks were able to seal oil and gas; 2） During the intense uplifting of the Devonian,the cap rocks with top surfaces at burial depths of 200-800 m and 500-1,100 m respectively were denuded in local areas,thus hydrocarbons trapped in earlier time were degraded to widespread bitumen; 3） In the hydrocarbon charging time of the Late Hercynian and Himalayan,the top surfaces of the cap rocks were at burial depths of over 2,000 m without intense uplifting and denudation thereafter,so trapped hydrocarbons were preserved.Based on cap rocks,the Ordovician Penglaiba Formation and Lower Cambrian dolomite could be potential targets for exploration on the Tazhong Northern Slope,and combined with hydrocarbon migration,less risk would be involved.     

Study of real-time LWD data visual interpretation and geo-steering technology

LWD（logging while drilling） data has been used to explore complex subtle reservoirs by realtime visual interpretation and geo-steering.The method comprises of computer communication,well log data processing,formation recognition,reservoir modeling and model updating in real time.We studied the key technologies related to real-time LWD data visual interpretation and geo-steering and developed computer software with Chinese intellectual property rights covering the following important aspects： 1） real-time computer communication of well site LWD data;2） visualization of geological model and borehole information;3） real-time interpretation of LWD data;4） real-time geological model updating and geo-steering technology.We use field application examples to demonstrate the feasibility and validity of the proposed technologies.     

A finite element model for analyzing horizontal well BHA behavior

Horizontal wells are proven to be better producers because they can be extended for a long distance in the pay zone. Engineers have the technical means to forecast the well productivity for a given horizontal length. However, experiences have shown that the actual production rate is often significantly less than that of forecasted. There are a number of reasons for the discrepancy of predicted to actual production rates in horizontal wells. However, it is a difficult task, if not impossible, to identify the real reason why a horizontal well is not producing what was forecasted. Often, the source of problem lies in the drilling of horizontal section such as permeability reduction in the pay zone due to mud invasion or snaky well patterns created during drilling. Although drillers aim to drill a constant inclination hole once in the pay zone, the more frequent outcome is a sinusoidal wellbore trajectory.Logging while drilling (LWD) and real time measurement of resistivity at bit help drill in the pay zone by constant monitoring of borehole trajectory and formation boundaries. Rotary steerable tools (RTS) allow spontaneous intervention to drilling direction and inclination if run with LWD tools. Nevertheless, there are still many cases where LWD cannot be deployed due to technical difficulties. One such case was noticed in the Middle East where LWD sensors were worn out completely during 1 h run time due to extreme formation abrasiveness. In the absence of LWD and RTS, it becomes a challenging task to drill a constant inclination borehole which will be addressed in this paper.The two factors, which play an important role in wellbore tortuosity, are the inclination and side force at bit. A constant inclination horizontal well can only be drilled if the bit face is maintained perpendicular to the longitudinal axis of bottom hole assembly (BHA) while keeping the side force nil at the bit. This approach assumes that there exists no formation force at bit. Hence, an appropriate BHA can be designed if bit side force and bit tilt are determined accurately.Finite element method (FEM) used in this study determines the bit side force and bit tilt simultaneously. The FEM is superior to existing analytical techniques because it can accommodate many more independent parameters which otherwise cannot be taken into account. As a matter of fact, it is believed that oversimplification of actual physical phenomena with unacceptable assumptions is the major source of error with existing BHA designs.This paper presents an FEM technique in assessing the bit tilt and side forces and compares the results with the existing techniques.     

水平井录井技术在华北油田的应用

在水平井钻进过程中,地质导向技术是保证井眼顺利着陆,并在油层中水平穿行一定距离的关键技术.针对华北油田水平井施工的技术特点,探讨了利用区域、邻井资料以及钻时、气测、岩屑等实时录井资料,结合MWD/LWD参数,较为精确地预测着陆点深度、地层倾角等目的层参数,以及判断钻头着陆和钻头在油层中位置的方法,在现场及时指导钻进方向,实现油层准确着陆、保障井眼轨迹尽可能多地位于油层中.在现场实践中效果显著,对今后的水平井施工具有重要的指导意义.     

页岩气水平井LWD曲线的环境因素影响及校正方法

随钻测井（LWD）曲线受环境因素影响不能准确反映页岩地层的实际特征,导致地质导向钻井精度不够,降低了优质页岩地层的钻遇率。以威远页岩气产业示范区水平井随钻测井曲线为研究对象,采用定量与定性相结合的方法评价了不同环境因素影响下随钻测井曲线的变化特征,构建了校正图版,利用最优拟合和数值迭代等方法建立图版公式化的校正模型,并结合室内页岩岩心数据进行可行性分析,最终形成了适用于页岩地层随钻测井曲线环境因素影响的校正方法。利用该方法处理了威远12口页岩气水平井的随钻测井资料,结果表明,校正后的随钻测井曲线消除了地层电性各向异性、相对夹角、井眼环境、仪器偏离间隙和钻井液密度等环境因素的影响,能够较好地反映所钻遇地层的实际特征。      

基于随钻测井资料的地层压力监测系统

提出了一种基于随钻测井资料的地层压力监测方法,能在钻井过程中利用随钻测井资料实时监测地层孔隙压力。首先,以WITS数据格式和TCP传输方式为基础开发了随钻测井数据实时采集程序,实现了随钻测井数据的实时采集;其次,根据邻近地区的已钻井资料建立初始压力监测模型,然后利用实时采集的随钻测井数据对目标井进行压力监测;最后,利用钻井过程中获取的地层压力信息(实测压力、钻井液密度等)对初始模型和压力计算结果进行校正,进而获取较为准确的地层压力监测结果。在理论研究的基础上开发了一套随钻地层压力监测系统软件,介绍了其主要功能模块。该监测系统在南海莺琼盆地进行现场应用,结果表明,系统能够准确监测地层压力,运行稳定、操作方便、监测精度较高,可以满足工程需要。     

A prediction method of borehole stability based on seismic attribute technology

Borehole instability in drilling engineering can bring about serious problems of drilling quality and safety. Based on the close relationships between seismic and well log information, the prediction method of borehole stability is presented to effectively control borehole instability. Conventional and nonlinear seismic attributes are extracted from borehole-side seismic traces of impending drilling well and drilled offset well respectively. Then the optimal attributes combinations sensitive to log properties are selected by using genetic algorithm and wavelet neural network technology together. A series of mapping models which reflect the nonlinear relationships between seismic attributes and acoustic and density log data of various formation intervals in drilled well are constructed through neural network modeling. With analysis of cutting logging data, seismic attributes of the formation under bit and corresponding mapping model can be used to predict acoustic and density log curves of this formation. Based on the predicted log data, log interpretation method, analysis technology of in-situ stress and mechanics model of borehole stability are employed to calculate in-situ stress, pore pressure, collapse pressure and fracture pressure, thus the safe drilling fluid density window which can keep borehole stable is determined. Prediction precision and real-time operation ability of the proposed method are satisfying, which have been proved in practical application in TR oil field.     

利用地震属性钻前预测井壁稳定性

钻前准确预测井壁稳定性是防止钻进过程中井壁失稳的有效手段。声波时差和地层密度是井壁稳定分析的两个关键参数。根据地震记录与地层声波时差及密度之间存在的非线性关系，提出了利用地震属性钻前预测井壁稳定性的方法。从井旁地震记录中提取地震属性，通过RBF神经网络在已钻井段的地震属性与声波时差及密度之间建立起映射模型，以此为基础预测待钻地层的声波时差和密度。运用预测结果结合井壁稳定力学模型，确定岩石力学参数和地应力状态，计算井壁坍塌压力和破裂压力，确定安全钻井液密度窗口，实现钻前井壁稳定预测。该方法在塔里木油田的应用中取得了良好的预测效果。