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.

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.

Research on High Temperature and High Density White Oil Based Drilling Fluid and Its Application in Well 201H7-6

As the depth and horizontal length of shale gas development wells increase,the requirement for the temperature resistance and the ability of the drilling fluids to stabilize the shale formation becomes higher.A new type of high temperature and high density white oil based drilling fluid system has been developed in laboratory.Research shows that the drilling fluid system has good rheological property,low filtration loss,strong anti-debris pollution capability and good plugging performance at high temperature and high density.The system has been successfully applied in the 201H7-6 well.Application results show that the drilling fluid rheology,high temperature and high pressure fluid loss and demulsification voltage meet the field requirements.The drilling fluid performance is stable in drilling an 1800 m horizontal section,and no stuck or shale swelling and wellbore collapsing are induced.It is the first well drilled successfully with domestic white oil-based drilling fluid in Zigong Region.It also sets several new records including the deepest well,the shortest drilling cycle,and the fastest drilling speed in that region,which provides valuable experience for the future drilling activities.

The utilization of spent palm cooking oil for formulating oil-based drilling muds with excellent H2S scavenging capability

In this study,a spent palm cooking oil-based mud with an excellent H2S scavenging capability induced by the inclusion of a small quantity of potassium permanganate is formulated and tested for the first time.The mud formulation,containing the spent palm oil as the continuous phase and water as the dispersed phase,respectively,was stabilized by Span 80 and rhamnolipid biosurfactant as primary and secondary emulsifiers,respectively,while hydrophobic zinc nanoparticles(NPs)were used as weighting agent.The results showed that H2S scavenging capacity at the breakthrough time reached 182.4 g H2S/barrel mud,which increased to 417.9 g H2S/barrel mud at the saturation time,demonstrating the effective H2S scavenging performance of the formulated mud.The spent palm oil-based mud(SPOBM)also showed a good flow behavior that could be well fitted using the Herschel-Bulkley and Casson models.The effect of temperature on the apparent viscosity of the SPOBM has been investigated,and the fitting of the viscosity-temperature data provided an estimate of the activation energy as 23.53 kJ/mol.The findings reported in this article reveal the feasibility of transforming the spent/waste cooking oils into a valuable commodity for formulating greener drilling fluids with acceptable rheology and excellent H2S scavenging performance.

Calculation and application of partition coefficients of light hydrocarbons in oil-based mud system

To find out the relationship between the oil-based mud,the formation fluid and the extracted gas,we use a thermodynamic approach based on static headspace gas chromatography technique to calculate the partition coefficients of 47 kinds of light hydrocarbons compounds between nC5 and nC8 in two kinds of oil-based mud-air systems,and reconstruct the original formation fluid composition under thermodynamic equilibrium.The oil-based drilling mud has little effect on the formation fluid compositions in the range of nC5-nC8(less than 1%for low-toxicity oil-based mud and less than 10%for oil-based mud).For most light hydrocarbon compositions,the partition coefficients obtained by vapor phase calibration and the direct quantitative methods have errors of less than 10%,and the partition coefficients obtained by direct quantitative method are more accurate.The reconstructed compositions of the two kinds of crude oil have match degrees of 91%and 89%with their real compositions,proving the feasibility and accuracy of reconstructing the composition of original formation fluid by using partition coefficients of light hydrocarbon compositions between nC5 and nC8.

加重剂对高密度白油基钻井液性能的影响

随着环保形势的日趋严峻,低毒性白油基钻井液在非常规油气藏钻井中逐渐得到广泛应用,而不同加重剂对白油基钻井液性能影响的系统研究较少。为此,本文在分析普通重晶石、微锰矿粉和毫微粉体3种加重剂粒径和形态的基础上,对比了3种加重剂单独加重以及微锰矿粉和普通重晶石复配加重形成的超高密度白油基钻井液的性能。结果表明:加重剂微观形态和粒径是钻井液性能差异的关键因素。当钻井液密度大于2.1g/cm^(3)时,微粉加重剂配制的高密度白油基钻井液流变性、润滑性和沉降稳定性优于普通重晶石,但中压失水量略高。按质量比1∶1将微锰矿粉与普通重晶石复配加重后,滤失量由6.0mL下降至3.6mL,弥补了微锰矿粉单一加重高密度白油基钻井液失水大的缺陷。重晶石和微粉加重剂复配加重是未来高密度油基钻井液、超高密度钻井液的发展方向。

非离子与阳离子表面活性剂协同改性白油基钻井液用蒙脱土

为了开发一种适用于白油的有机土并应用在海上高温高压地层环境,本文通过使用非离子表面活性剂与阳离子表面活性剂对蒙脱土协同改性,采用湿法工艺制得有机土DMOS。选择了其他两种在现场使用的柴油基钻井液有机土与其做性能对比评价。结果表明,非离子与阳离子表面活性剂协同改性的蒙脱土片晶疏松,与白油的接触角极小。有机土DMOS在白油中具有很好的成胶性能,在140℃的条件下,胶体率仍能保持在94%。基于DMOS配置的油基钻井液具有更为稳定的流变性能,在140℃的条件下保持高于1000V的电稳定性。所形成的低渗低厚度泥饼以及良好的润滑性能够减少钻具与井壁的摩擦,防止卡钻,可满足海上现场钻井需求。

环保型白油基钻井液研究和应用进展

白油为基液的环保型油基钻井液有助于解决井壁坍塌问题。本文介绍了环保型白油基钻井液在水平井、高温深井、大位移定向井、深水井及复杂地层钻探中应用现状,并提出了环保型白油基钻井液面临的问题及今后的研究方向,以期为国内钻井液技术的发展提供参考。

国内外油基钻井液研究现状

油基钻井液具有抗侵蚀、抗高温、润滑性好、有利于井壁稳定以及对储层污染程度小等特点,主要用于地层情况复杂的深井、超深井和水平井等。主要介绍了国内外油基钻井液的研究现状,油基钻井液按基油类型可分为四类:白油基钻井液、柴油基钻井液、气制油基钻井液、低毒钻井液。对各类油基钻井液进行了评价与比较,并对油基钻井液今后的发展提出了建议。

白油基钻井液体系研究与应用

基于油基钻井液良好的抗高温稳定性、良好的润滑性、抗污染能力和油层保护效果,其越来越多的应用在油气田开发过程。而柴油基钻井液使用造成的生态环境污染影响制约着其推广应用。为了满足保护生态和勘探开发的需要,室内成功研究出了以低毒矿物油白油为基油的油基钻井液。现场应用三口水平井,维护简单、性能稳定,起下钻畅通、钻进正常,有效解决了水平段泥页岩的水敏掉块、托压等问题。圆满完成了钻探任务,现场取样测试其油气层静态渗透率恢复值均在在90%以上。

钻井液用缓释复合消泡剂的研制与应用

目前国内市场上钻井液消泡剂品种少、适用范围窄、有效作用时间短，本文报道一种适用于多种钻井液的缓释型复合消泡剂。该剂制备方法如下：硬脂酸铝、二甲基硅油及白油在120反应2小时，冷却后加25％--30％乳化剂制成乳状液，再加入微胶囊化剂，在高剪切力作用下制成微胶囊化消泡剂。乳状液可维持稳定60天以上。该剂在加入ABS发泡的淡水、4％盐水、饱和盐水基浆中的综合消泡性能好于醚类、酯类和醇类消泡剂。在聚磺、聚合物和饱和盐水凹凸棒实验钻井液中，该荆消泡性能好，对钻井液常规性能无影响，还有减摩阻作用。在聚合醇和钙基实验钻井液中，加入该剂0．07％时密度恢复率超过90％。在聚磺实验钻井液中，该剂在150℃仍具有良好的消泡和抑泡效果。该剂在已在国内许多大油田获得应用。大港板深22井2005～5127m井段使用的高温有机硅钻井液，由于加入了磺化类、腐殖酸类、树脂类处理剂而产生了气泡，加入该剂0．2％--0．3％后迅速消泡，密度恢复原值（1．18～1．52g／cm^3），处理一次可维持4～5天不起泡，井深5100m时井底温度175℃，循环钻井液温度约165℃，该剂消泡性能仍良好。表9参5。

低芳烃油基钻井液在页岩油气水平井中的应用

国内外页岩油气水平井大部分使用柴油基钻井液,例如胜利油田第一口页岩油水平井渤页平1井,柴油具有刺激性气味,含有一定的芳香烃,对人体健康存在一定伤害,因此开展了低芳烃油基钻井液研究。通过室内实验,选定芳烃含量小于2%的精制白油作基油,确定油水比为80∶20,优选了相配套主处理剂及其加量,形成了低芳烃油基钻井液配方。室内评价结果表明,该钻井液在1.20～1.80 g/cm3的不同密度下都具有较好的流变性能、乳化性能和沉降稳定性,抗污染能力强,由于使用刚性、柔性和树脂类封堵材料的复合处理剂作封堵剂,该钻井液封堵能力强。该钻井液在渤页平2井进行了成功应用,钻井液日损耗量明显降低,应用井段平均机械钻速达8.22 m/h,较渤页平1井有了大幅提高;井径规则,井径扩大率仅为2.3%;无托压现象、扭矩小,起下钻摩阻小(7～8 t)。该钻井液满足页岩油气藏水平井钻井施工需要,而且对对人体健康影响较小。

白油中高成胶率有机土HMC-4的研究

有机土是油基钻井液中一种亲油胶体,主要功用是增黏提切和降滤失。目前常规有机土在芳香烃含量高的柴油中成胶性能好,而在芳香烃含量低的白油或气制油中成胶性能则差;但是柴油的生物毒性较大,随着人类环保意识的增强,在钻井液中使用柴油作为基础油受到了很大的限制,而将更多使用生物毒性小的白油或气制油。针对常规有机土在白油或气制油中成胶性能差的问题,通过优选土粉、有机覆盖剂及工艺条件,采用干法工艺制得有机土HMC-4,并对其性能进行了评价。结果表明,有机土HMC-4在5#白油中具有好的成胶性能,胶体率可达72%。以5#白油为基础油,由有机土HMC-4配制的全油基钻井液具有较高的切力和较低的滤失量,使钻井液具有了较好的稳定性和携岩性,可满足钻井工程要求。

河南油田泌页2HF井钻井液技术

河南油田泌阳凹陷是中石化非常规勘探开发的重点区域之一,在该地区已钻的泌页HF1井泥岩段多次发生钻头泥包、页岩段塌卡频繁等问题,为此,泌页2HF井二开造斜段选用聚胺钾基钻井液体系,并通过沥青、石蜡和无渗透剂的有效封堵及合适的钻井液密度对井壁形成有力支撑,解决了因地层分散引起的钻头泥包及页岩垮塌问题;且在三开段选用白油基钻井液体系,有力保障了纯页岩、长水平段水平井施工的安全。全井未发生一次钻头泥包,井壁稳定,起下钻顺利,安全无事故。

环保型全白油基钻井液的研究与应用

随着油基钻井液在国内外的使用规模越来越大,室内优选出了2套密度达到2.0 g/cm3、抗温能力达到150℃的全白油基钻井液的基础配方,并于2009年率先在中国辽河油田沈307井3 709～4 146 m井段进行了现场应用。结果表明,该全油基钻井液具有较好的流变性、沉降稳定性、剪切稀释性以及优良的悬浮和携带固相的能力,滤失量低,满足了现场施工的要求;具有较强的抗水侵(20%水)和抗土污染能力(15%劣质土);该钻井液在沈307井三开井段的使用性能良好,机械钻速高。全白油基钻井液在沈307井的成功应用,为长城钻井液公司进一步拓展海外油基钻井液市场奠定了坚实的技术基础。

高温高压全油基钻井液流变性研究与评价

选用Rheo-Stress 6000型高温高压流变仪,测定不同密度、不同温度(60℃、120℃、150℃、180℃和200℃)和压力梯度下白油全油基钻井液的流变特性。实验结果表明,无论哪种密度的油基钻井液,温度升高都使其表观粘度、剪切应力降低,压力增加都使其增大:150℃的高温下,随着压强的增加,钻井液粘度增幅越来越小,后期趋于平缓,温度和压力同时作用于钻井液流体时,温度占主导作用;在较高的压力和温度下,白油全油基钻井液体系仍有很好的塑性粘度和动切力;此配方白油全油基钻井液在高温高压条件下体系稳定,剪切稀释性好。

柴油和白油基钻井液用有机土性能研究

本文报道的柴油基有机土(DB)由钠基膨润土(NB)和季铵盐型表面活性剂制成,白油基膨润土(WB)由NB和季铵盐型表面活性剂、功能化聚合物制成。采用XRD、FTIR、SEM、TEM方法对两种油基钻井液用有机土进行了表征,结果表明插层剂已进入蒙脱石晶层间,在蒙脱石晶层表面发生化学键连;NB、DB、WB的晶层间距分别为1.22、2.49、2.67 nm;有机土层片堆砌变疏松,WB层片的堆砌较DB更为疏松。DB在柴油中、WB在白油中胶体率均达100%,显示良好的耐高温性能,220℃热滚16 h后表观黏度、塑性黏度和动切力分别为15和19 mPa.s,9和15mPa.s,6和4 Pa。WB在柴油中同样具有良好的凝胶和流变性能,DB在白油中胶体率较低,流变性能较差。