页岩储层纳米钻井液暂堵机理研究

发布时间：2018-06-24 16:47

本文选题：页岩 + 纳米暂堵　；参考：《成都理工大学》2017年硕士论文

【摘要】：我国页岩气资源量巨大,发展前景广阔,开发过程中投入巨大,而产出相对较小,其中一个很重要的原因是页岩基质纳米孔隙发育,工作液在毛细管力作用下源源不断进入储层,与黏土矿物作用,容易导致井壁失稳、储层损害等问题。目前,页岩储层钻井过程中主要采用油基钻井液,但其成本高,污染环境,侵入储层后难返排,储层损害严重。为了降低工作液滤液向页岩储层的滤失,确立了利用酸溶性纳米材料暂堵纳米孔隙的思路。在评价龙马溪组露头页岩的物性参数、矿物组成、孔径分布及其对渗透率贡献率的基础上,优选了油湿型纳米碳酸钙为纳米添加剂及十六烷基三甲基氯化铵为分散剂,在此基础上配制的纳米钻井液的表观粘度、塑性粘度和动切力随纳米颗粒及十六烷基三甲基氯化铵浓度的增大均先增大后降低,当纳米颗粒浓度为2%时达到最大值,API滤失量随纳米颗粒浓度的增大而逐渐降低。提出了基于压力传递法测试基质型岩心液体渗透率,并以此评价了各因素对封堵及解堵效果的影响。实验结果表明:纳米颗粒浓度为1%时,封堵效果较好,且随着封堵时间的延长,岩心渗透率迅速降低,之后趋于平缓;压差为2MPa条件下,利用15%的稀盐酸酸蚀30分钟后岩心渗透率恢复率达到83.91%~87.50%,解堵效果良好。此外,设计实验研究了毛细管力及压差对钻井液滤液以及纳米颗粒进入基质孔隙的影响,结果表明当岩心含水饱和度较小时,毛细管力起主要作用,随着含水饱和度的逐渐增大,压差的作用逐渐增强。纳米钻井液封堵页岩基质孔隙过程中,对于与纳米颗粒尺寸相仿的孔隙,纳米颗粒以“卡喉”形式实现封堵,对于尺寸较大的孔隙,纳米颗粒以架桥形式实现封堵。纳米钻井液暂堵等效宽度为1μm左右的微裂缝实验结果表明:纳米颗粒浓度为4%时钻井液可以实现有效封堵,且随着封堵时间的延长,渗透率迅速降低,之后趋于平缓;压差为2MPa时,利用15%的稀盐酸酸蚀解堵,渗透率恢复率随酸蚀时间延长而增大,1h后渗透率恢复到原始渗透率的68.09%~74.19%;增大返排压力可以进一步提高岩心的渗透率恢复率,当压差达到8MPa时,渗透率恢复率突然增大的85.11%,达到较好解堵效果。纳米钻井液封堵微裂缝过程中,尺寸较大的颗粒与纳米颗粒堆积在微裂缝端部,且纳米颗粒充填在大颗粒堆积后剩余的空间,使封堵带更加致密,使渗透率降低,且大量的纳米颗粒与少量的尺寸相对较大但比微裂缝宽度小的颗粒进入微裂缝,进一步降低微裂缝的渗透率。
[Abstract]:In China, shale gas resource is huge, the development prospect is broad, the investment in the development process is huge, but the output is relatively small, one of the important reasons is the development of shale matrix nano-pores. The working fluid enters the reservoir continuously under the action of capillary force, and the interaction with clay minerals can easily lead to wellbore instability and reservoir damage. At present, oil based drilling fluid is mainly used in the drilling process of shale reservoir, but its cost is high, the environment is polluted, it is difficult to return to discharge after invading the reservoir, and the reservoir damage is serious. In order to reduce the filtration loss of the filtrate from the working fluid to the shale reservoir, the idea of temporarily plugging the nanometer pore with the acid soluble nanomaterials was established. Based on the evaluation of physical parameters, mineral composition, pore size distribution and permeability contribution of outcrop shale in Longmaxi formation, oil wet nano-calcium carbonate was selected as nanometer additive and cetyltrimethylammonium chloride as dispersant. On this basis, the apparent viscosity, plastic viscosity and dynamic shear force of the nano-drilling fluid increased firstly and then decreased with the increase of the concentration of nano-particles and cetyltrimethylammonium chloride. When the concentration of nanoparticles is 2, the maximum value of API loss decreases with the increase of the concentration of nanoparticles. Based on the pressure transfer method, the liquid permeability of the matrix core is measured, and the influence of various factors on the plugging and plugging removal is evaluated. The experimental results show that when the concentration of nanoparticles is 1, the plugging effect is better, and with the prolongation of plugging time, the core permeability decreases rapidly and then tends to smooth, and the pressure difference is 2 MPA. The recovery rate of core permeability is 83.91and 87.50 after 30 minutes of acid etching with 15% dilute hydrochloric acid, and the plugging removal effect is good. In addition, the effects of capillary force and pressure difference on the flow of drilling fluid filtrate and nanoparticles into the matrix pore are studied experimentally. The results show that the capillary force plays a major role when the saturation of water in the core is small. With the increase of water saturation, the effect of pressure difference increases gradually. In the process of plugging shale matrix pores with nano-drilling fluid, the nano-particles can be blocked in the form of "clamping throat" for pores similar to the size of nano-particles, and for larger pores, nano-particles can be blocked in the form of bridging. The experimental results of microfracture with the equivalent width of about 1 渭 m for temporary plugging of nano-drilling fluid show that the drilling fluid can be effectively plugged when the concentration of nanoparticles is 4 渭 m, and the permeability decreases rapidly with the prolongation of plugging time, and then tends to smooth; When the pressure difference is 2 MPA, using 15% dilute hydrochloric acid to remove the plugging, the permeability recovery rate increases with the increase of acid etching time for 1 hour, and the permeability returns to 68.09% 74.19% of the original permeability, and the permeability recovery rate of the core can be further improved by increasing the backflow pressure. When the pressure difference reaches 8 MPA, the permeability recovery rate increases suddenly 85.11%, and the plugging removal effect is better. In the process of plugging micro-fracture with nano-drilling fluid, the larger particles and nanoparticles are stacked at the end of the micro-fracture, and the nano-particles fill the remaining space after the accumulation of large particles, which makes the plugging zone denser and the permeability lower. A large number of nanoparticles and a small number of particles which are relatively larger in size but smaller in the width of the microfracture enter into the microfracture and further reduce the permeability of the microfracture.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE254

【参考文献】