Evaluación reológica de fluidos de perforación base agua con nanosílice

ABSTRACT Generally, drilling fluids may be defined as fluids with a composition that can assist the generation and removal of cuttings from the borehole to the surface. They are classified according to their base as water based mud (WBM), oil based mud (OBM) or gas. Polymers, densifiers, brines, surfactants, among others are the primary components of drilling fluids. Currently the trend is to develop WBMs, which simulate the high performance of OBMs, with benefits such as reduction of environmental impacts and lower costs associated with cuttings and fluids disposal. This challenge introduces high performance materials in the oil industry such as nanomaterials. The increasing demand of hydrocarbons has led the study and production of unconventional resources in Argentina and worldwide like shale and tight reservoirs. Shales are sedimentary rocks composed of clay size particles and organic matter with laminar structure, low permeability and nanopores. In these types of rocks wellbore stability and shale inhibition are key factors while drilling with WBM, so it is necessary to avoid pore pressure increase and subsequent penetration of drilling fluid into the formation. In this research nanosilica (12nm) was used to minimize shale permeability through physically plugging the nanopores of shales which are of 30 nm as average. This nanomaterial will minimize not only fluid penetration, pore pressure, shale permeability and fluid-rock interaction but will improve wellbore stability. In this work the rheological behavior of WBM with nanoparticles was analyzed. Fluids were prepared with the same additives and composition as the ones used in argentine fields. Finally, the rheological behavior of WBM was compared with the OBM´s and the best concentration of nanosilica was determined: 0,5 %p/p. Also, filtration and inhibition tests were performed in agreement with API 13B1-2 and API 13I.

摘要 通常而言，钻井液可定义为一类具备特定组成的流体，其核心功能是辅助生成并将井眼产生的岩屑携带至地面。钻井液按基液类型可分为水基钻井液（WBM）、油基钻井液（OBM）以及气体钻井液三类。聚合物、加重剂、盐水、表面活性剂等均为钻井液的主要组成成分。当前行业发展趋势为研发性能可媲美油基钻井液的水基钻井液，其优势在于可降低环境影响，同时削减岩屑与钻井液处理相关的成本。这一行业需求推动了纳米材料等高性能材料在石油工业中的应用。全球范围内对烃类资源的需求持续增长，推动了阿根廷及全球各地页岩、致密储层等非常规油气资源的勘探开发研究。页岩是由黏土级颗粒与有机质构成的沉积岩，具备层状结构、低渗透率与纳米孔隙的特征。在该类储层中使用水基钻井液钻进时，井眼稳定性与页岩抑制性为核心关键因素，因此需避免孔隙压力升高以及钻井液后续侵入地层。本研究采用粒径为12nm的纳米二氧化硅（nanosilica），通过物理封堵平均孔径约30nm的页岩纳米孔隙，以降低页岩渗透率。该纳米材料不仅可减少流体侵入、孔隙压力升高、页岩渗透率提升与流体-岩石相互作用，还能改善井眼稳定性。本研究分析了添加纳米颗粒的水基钻井液的流变性，实验所用钻井液的添加剂与组成与阿根廷油田实际使用的钻井液一致。最后，将该纳米改性水基钻井液的流变性与油基钻井液进行对比，并确定了纳米二氧化硅的最优添加浓度：0.5%质量比。此外，本研究依据API 13B1-2与API 13I标准开展了滤失与抑制性测试。