Gas-hydrate formation,agglomeration and inhibition in oil-based drilling fluids for deep-water drilling

One of the main challenges in deep-water drilling is gas-hydrate plugs,which make the drilling unsafe.Some oil-based drilling fluids（OBDF） that would be used for deep-water drilling in the South China Sea were tested to investigate the characteristics of gas-hydrate formation,agglomeration and inhibition by an experimental system under the temperature of 4 ？C and pressure of 20 MPa,which would be similar to the case of 2000 m water depth.The results validate the hydrate shell formation model and show that the water cut can greatly influence hydrate formation and agglomeration behaviors in the OBDF.The oleophobic effect enhanced by hydrate shell formation which weakens or destroys the interfacial films effect and the hydrophilic effect are the dominant agglomeration mechanism of hydrate particles.The formation of gas hydrates in OBDF is easier and quicker than in water-based drilling fluids in deep-water conditions of low temperature and high pressure because the former is a W/O dispersive emulsion which means much more gas-water interfaces and nucleation sites than the later.Higher ethylene glycol concentrations can inhibit the formation of gas hydrates and to some extent also act as an anti-agglomerant to inhibit hydrates agglomeration in the OBDF.

Rheological properties of oil-based drilling fluids at high temperature and high pressure

The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.

Squeeze-Strengthening Effect of Silicone Oil-based Magnetorheological Fluid

In order to study the squeeze-strengthening effect of silicone oil-based magnetorheological fluid （MRF）, theoretical basis of disc squeezing brake was presented and a squeezing braking characteristics test-bed for MRF was designed. Moreover, relevant experiments were carded out and the relationship between squeezing pressure and braking torque was proposed. Experiments results showed that the yield stress of MRF improved linearly with the increasing of external squeezing pressure and the braking torque increased three times when external squeezing pressure achieved 2 MPa.

Comparison and application of different empirical correlations for estimating the hydrate safety margin of oil-based drilling fluids containing ethylene glycol

As the oil and gas industries continue to increase their activity in deep water, gas hydrate hazards will become more serious and challenging, both at present and in the future. Accurate predictions of the hydrate-free zone and the suitable addition of salts and/or alcohols in preparing drilling fluids are particularly important both in preventing hydrate problems and decreasing the cost of drilling operations. In this paper, we compared several empirical correlations commonly used to estimate the hydrate inhibition effect of aqueous organic and electrolyte solutions using experiments with ethylene glycol （EG） as a hydrate inhibitor. The results show that the Najibi et al. correlation （for single and mixed thermodynamic inhibitors） and the Ostergaard et al. empirical correlation （for single thermodynamic inhibitors） are suitable for estimating the hydrate safety margin of oil-based drilling fluids （OBDFs） in the presence of thermodynamic hydrate inhibitors. According to the two correlations, the OBDF, composed of 1.6 L vaporizing oil, 2% emulsifying agent, 1% organobentonite, 0.5% SP-1, 1% LP-1, 10% water and 40% EG, can be safely used at a water depth of up to 1900 m. However, for more accurate predictions for drilling fluids, the effects of the solid phase, especially bentonite, on hydrate inhibition need to be considered and included in the application of these two empirical correlations.

Development of a High Temperature and High Pressure Oil-Based Drilling Fluid Emulsion Stability Tester

When drilling deep wells and ultra-deep wells, the downhole high temperature and high pressure environment will affect the emulsion stability of oil-based drilling fluids. Moreover, neither the demulsification voltage method nor the centrifugal method currently used to evaluate the stability of oil-based drilling fluids can reflect the emulsification stability of drilling fluids under high temperature and high pressure on site. Therefore, a high-temperature and high-pressure oil-based drilling fluid emulsion stability evaluation instrument is studied, which is mainly composed of a high-temperature autoclave body, a test electrode, a temperature control system, a pressure control system, and a test system. The stability test results of the instrument show that the instrument can achieve stable testing and the test data has high reliability. This instrument is used to analyze the factors affecting the emulsion stability of oil-based drilling fluids. The experimental results show that under the same conditions, the higher the stirring speed, the better the emulsion stability of the drilling fluid;the longer the stirring time, the better the emulsion stability of the drilling fluid;the greater the oil-water ratio, the better the emulsion stability of the drilling fluid. And the test results of the emulsification stability of oil-based drilling fluids at high temperature and high pressure show that under the same pressure, as the temperature rises, the emulsion stability of oil-based drilling fluids is significantly reduced;at the same temperature, the With the increase in pressure, the emulsion stability of oil-based drilling fluids is in a downward trend, but the decline is not large. Relatively speaking, the influence of temperature on the emulsion stability of oil-based drilling fluids is greater than that of pressure.

Development of key additives for organoclay-free oil-based drilling mud and system performance evaluation

Traditional oil-based drilling muds(OBMs) have a relatively high solid content, which is detrimental to penetration rate increase and reservoir protection. Aimed at solving this problem, an organoclay-free OBM system was studied, the synthesis methods and functioning mechanism of key additives were introduced, and performance evaluation of the system was performed. The rheology modifier was prepared by reacting a dimer fatty acid with diethanolamine, the primary emulsifier was made by oxidation and addition reaction of fatty acids, the secondary emulsifier was made by amidation of a fatty acid, and finally the fluid loss additive of water-soluble acrylic resin was synthesized by introducing acrylic acid into styrene/butyl acrylate polymerization. The rheology modifier could enhance the attraction between droplets, particles in the emulsion via intermolecular hydrogen bonding and improve the shear stress by forming a three-dimensional network structure in the emulsion. Lab experimental results show that the organoclay-free OBM could tolerate temperatures up to 220 ?C and HTHP filtration is less than 5 m L. Compared with the traditional OBMs, the organoclay-free OBM has low plastic viscosity, high shear stress, high ratio of dynamic shear force to plastic viscosity and high permeability recovery, which are beneficial to penetration rate increase, hole cleaning and reservoir protection.

HI-OILFREE钻井液技术

大庆长垣外预探水平井具有油层物性和连续性差、储层辨识难度大、水平位移长、钻井周期长,储层含有大段泥页岩等技术难点。以往使用油包水钻井液施工,环境保护及成本压力较大,后期回收处理难度高。因此,室内优选出了HI-OILFREE钻井液,该钻井液利用胺基抑制剂AP-1对泥页岩及黏土的优良抑制作用及阳离子聚合物CAL-90对黏土的高效端面吸附作用控制水化及维护井眼稳定;利用极压润滑剂HLX-069、白油和乳化剂、固体润滑剂MRH的协同作用提高钻井液润滑性;用硅类表面活性剂作防水锁剂。室内评价及龙平1井的现场应用表明,HI-OILFREE钻井液抑制性强、流变性好、润滑效果好,荧光级别小于5,现场维护处理工艺简单,能够满足水平井钻井施工要求,储层保护效果显著,且成本与油包水钻井液相比下降了70%。

增效型无土相仿生油基钻井液技术的研究与应用

针对深井超深井钻井过程中钻遇高温高压、井壁失稳及井下复杂情况的难题,基于仿生学、超分子化学以及岩石表面润湿性理论,通过优选仿生增效剂、仿生提切剂及仿生降滤失剂,配套相关处理剂,最终形成了一套适用于深井、超深井地层钻探的增效型无土相仿生油基钻井液体系。研究发现,建立的增效型无土相仿生油基钻井液体系可抗220℃高温,配制密度为2.4 g/cm^(3),破乳电压大于400 V,高温高压滤失量为3.2 mL,人造岩心在该体系中220℃下老化后的抗压强度达到7.1 MPa,平均渗透率恢复值为93.9%。现场应用情况表明,体系流变性能稳定,平均机械钻速比邻井提高16%,平均井径扩大率仅为1.25%,可有效解决深井超深井钻井过程中出现的井壁失稳难题,为我国深井超深井的钻探提供了技术保障。

井研地区筇竹寺组页岩储层水平井钻井井壁稳定性评价

川西南井研区块筇竹寺组页岩气具有良好的开发前景,但由于对其岩矿组分、力学性质、水化特征等认识程度较低,钻井井壁稳定性认识不清,导致出现掉块、阻卡等复杂情况。为了充分认识该区寒武系筇竹寺组地层的井壁稳定性,明确粉砂质页岩水化作用及其对坍塌压力的影响规律,在岩石力学实验的基础上,研究不同钻井液浸泡时间对岩石力学参数的影响规律,建立考虑水化作用的井壁稳定性预测模型,分析不同井斜方位下坍塌压力的差异。研究结果表明:筇竹寺组伊蒙混层含量高,具有一定膨胀性,水化作用后导致岩石强度降低,对井壁稳定性有较大影响;不同钻井液体系对井壁稳定性的影响有差异,总体上油基钻井液更有利于井壁稳定;考虑了水化作用的井壁稳定预测模型更加符合实际,以此为依据,通过优化钻井液设计可以有效降低井壁失稳风险,提高钻井时效。

负压振动筛原理及在油基钻井液钻屑减量中的应用

经过几十年的发展,振动筛性能有很大提高,但其对钻屑的脱液能力已达极限。40年来,应用于钻井固控,效果不明显。十多年前,经过尝试与高频低幅振动相结合的真空过滤技术应用于钻井固控时,钻屑的脱液能力显著提高,排放钻屑体积大幅减小。近年来,多种负压振动筛在国内钻井中开展了应用试验。经过对常规振动筛复合负压过滤的负压振动筛的原理、主要技术参数、现场应用与国内外类似技术的对比分析及现场应用表明,所使用的负压振动筛的处理量、钻屑含液率、钻屑排放减少量、筛网寿命、能效、设备成本、使用经济效益等都均有明显优势。负压振动筛的应用对节能减排和实现“碳中和”具有重要作用,其逐渐替代常规振动筛,将是钻井固控技术发展的必然趋势。

亲油水泥浆界面封隔性能评价研究

页岩气井油基钻井液条件下固井时,套管与井壁表面附着油膜或油基钻井液易导致水泥环界面封隔能力下降,形成窜流通道,影响后期增产改造作业。虽然前置液能有效提高界面润湿反转,但受用量、冲洗效率等因素限制,界面仍会出现油膜附着情况。为此,在水泥浆中加入亲油表面活性剂,制备形成亲油水泥浆,赋予水泥环亲油能力。采用接触角、剪切胶结强度、界面水力封隔测试等评价了亲油水泥石的亲油能力及界面封隔效果。研究发现,非极性溶剂在亲油水泥石表面接触角远低于常规水泥石表面,具备良好的亲油性能;亲油水泥石与含白油、油基钻井液的套管、页岩岩芯胶结后,一、二界面抗流体窜流压力分别提升500%和400%,胶结强度分别提高205%和122%;亲油表面活性剂的加入不会对水泥水化程度、水泥浆工程性能及水泥石力学性能产生负面影响。结果表明,亲油表面活性剂掺入后可有效提高水泥环与含油界面的封隔能力,具备提高油基钻井液条件下水泥环套管地层界面胶结与封隔性能的潜力。

页岩油储层环保型高性能水基钻井液体系研究及应用

为了满足页岩油储层钻井对钻井液环保性能的要求,以环保型页岩抑制剂HBY-S和环保型复合润滑剂HBR-L为主要处理剂,并结合其他环保型处理剂,研制出了一种适合页岩油储层钻井的环保型高性能水基钻井液体系。室内对钻井液体系的耐温性能、抗污染性能和环保性能进行了评价,结果表明:体系具有良好的耐温性能,经过160℃老化后钻井液体系的高温高压滤失量为9.6mL,岩屑滚动回收率可以达到90.6%,润滑系数为0.089;体系具有较强的抗污染能力,钻井液中加入10%NaCl、1.0%CaCl_(2)或者15%岩屑粉时流变性能和滤失性能均比较稳定;体系的环保性能优良,钻井液的EC_(50)值为85000(无毒),BOD_(5)/COD值为26.5%(易降解),重金属含量均低于行业标准值。环保型高性能水基钻井液在某页岩油区块水平井钻井过程中进行了成功应用,其中DG-1井钻井期间未出现井下复杂事故,现场钻井液性能稳定,环保性能达标,实现了安全高效钻井的目标,在页岩油水平井钻井中具有良好的推广应用前景。

有机层状硅酸盐改善油基钻井液沉降稳定性室内评价

基于油基钻井液有机土有机改性剂阳离子受高温易分解脱附,引起钻井液性能变差、加重材料沉降等问题,利用六水合氯化镁和十六烷基三甲氧基硅烷等为原料,合成了一种适用于柴油基钻井液体系的有机土(有机层状硅酸盐),用于改善油基钻井液的沉降稳定性;通过傅里叶红外光谱、X-射线衍射以及室内钻井液沉降实验进行结构表征和沉降稳定性评价。结果表明:该有机硅酸盐材料具备2∶1层状硅酸盐结构和以Si—C共价键连接的不对称链状有机官能团结构,且300℃无明显热分解;相比于大庆油田常用油基钻井液,该有机层状硅酸盐提高了油基钻井液的动切力、动塑比和储能模量,明显改善了1.4~2.0 g·cm^(-3)密度范围、150℃以下老化温度油基钻井液的悬浮性能和沉降稳定性能。

抗高温油基钻井液的室内研究与应用

针对YJ3-X超深大斜度井三开井段存在的裂缝发育、井漏风险高、斜井段位移长、携砂困难、摩阻扭矩大、完井下套管作业时间长等钻完井难题,室内通过乳化剂的优选对现有抗高温油基钻井液体系配方进行了优化,并根据临井出现的复杂情况模拟该井可能出现的风险,评价了优化后钻井液体系的抗岩屑污染和盐水污染性能。试验结果表明,优化后的抗高温油基钻井液具有良好的流变性,抗温达180℃,破乳电压高达1366 V,高温高压滤失量低至2 mL,抗岩屑污染达20%,抗CaCl2盐水污染达30%,静置120 h后沉降因子为0.52,可满足井下各类复杂环境的作业需求。现场应用效果表明,优化后的抗高温油基钻井液流变性稳定,具有较低的黏度和较强的触变性,井眼清洁良好,起下钻和下套管摩阻低,井壁稳定,较好地满足了YJ区块大斜度深井作业需求。

近油基钻井液在文23储气库水平井的应用

中原文23储气库沙四段采用φ235.00 mm钻头,利于注气,但水平井钻井存在以下难题:泥岩含量高,井壁易失稳;非常规井眼携岩带砂难度大;短半径水平井模式,狗腿度大,定向易托压。采用机理和性能与油基钻井液相当的环保型近油基钻井液有助于解决以上难题,现场应用2口井,结果表明:(1)该钻井液对沙四段泥岩井壁稳定周期长;(2)润滑性好,定向无托压,起下钻摩阻低;(3)钻井液携岩能力强,井眼清洁效果好。缩短了钻完井周期,降低了钻井成本,对文23储气库部署具有重大意义。

油基钻井液乳化剂的制备与性能评价

钻井液乳化剂是油井钻探中的重要化学品之一,其性能评价对于钻井工程的成功进行具有重要意义。优秀的乳化剂能确保钻井液的稳定性和流变性能。在选择乳化剂时,应充分考虑其理化性能和体系综合性能,以确保钻井工程的成功进行。本研究以植物油酸、二乙烯三胺、马来酸酐为主要原料,制备了6种乳化剂产品,并对其进行理化性能评价和体系综合性能评价。实验结果显示,乳化剂PF-MOEMUL1、PF-MOCOAT1、PF-MOEMUL2、PF-MOCOAT2满足所有指标要求,在理化性能评价和体系综合性能评价的关键指标上有良好的性能,为钻井工程提供可靠的保证。而乳化剂PF-MOEMUL3、PF-MOCOAT3在倾点和塑性黏度方面未能达到指标要求。可能导致乳液不稳定、流变性能不佳等问题,从而影响钻井工程的顺利进行。通过对钻井液乳化剂的性能评价,对乳化剂的选择和应用提供了有效的参考指导。

溱潼凹陷红页201井组钻完井关键技术研究与应用

溱潼凹陷红页201井组以定向井方式开发页岩油,通过井身结构优化,形成二开制(变径)井身结构,优选高效钻头复合钻井技术(PDC)钻头实现钻井提速,使用偏心扩眼器应对上部井段缩径问题,优选高性能水基钻井液体系维持井壁稳定,实现红页201井组高效钻完井。

高阻地层HDIL阵列感应影响因素分析与校正方法

近年来,四川盆地川中深层灯影组和龙王庙组天然气勘探中越来越多地使用油基泥浆,使得裸眼井电阻率测井只能选择阵列感应仪器。该地区目的层致密碳酸盐岩普遍表现为中高电阻率,典型气层的电阻率一般在500Ω·m以上甚至高达2000Ω·m,使得测量电导率的感应测井仪器接收的信号弱,叠加深层高温等因素的影响,采集的信号常出现负值,软件聚焦处理结果常出现平头现象,不能用于储层识别和气层评价。采用有限元模拟算法,分析泥浆电阻率、侵入半径及原状地层电阻率等单因素对阵列感应测井响应的影响规律,明确了各环境因素对感应测量信号的影响规律。结果表明,地层与泥浆电阻率对比度对测量信号有明显影响,当对比度接近于1时,各子阵列的误差较小,而侵入深度是另一个重要影响因素。总体上,较长源距的子阵列受各种因素的影响相对较小。针对实际资料的特点,提出一种基于Archie公式的原始电导率信号约束校正方法,对约束校正后的数据再开展软件聚焦,其结果得到明显改善。

超支化絮凝剂对废弃油基钻井液的絮凝效果评价

油基钻井液受地层土等劣质固相的不断侵入,流变性能严重恶化,采用溶剂萃取、热蒸馏等技术难以有效处理,会造成资源浪费。为实现对废弃油基钻井液的再生利用,本文选取超支化聚合物作为絮凝主剂,进行季铵化和疏水改性,制得具备良好选择性的油溶性絮凝剂;通过红外光谱、热重分析等方法测定了絮凝剂分子的结构与热稳定性,探究了絮凝剂加量对钻井液密度、固相含量和流变性能的影响,通过zeta电位和矿物组分分析,进行了絮凝剂的絮凝机理分析。结果表明:絮凝剂加量1.0‰时,可有效絮凝、沉淀钻井液体系中的劣质固相,对两种油基钻井液废液处理后固相清除率可达到80.6%和63.8%,处理后钻井液密度分别为0.733g/cm^(3)和0.745g/cm^(3),其配伍性和流变性能满足钻井要求,可实现钻井液的再生循环利用。