Optimization of an in-situ polymerized and crosslinked hydrogel formulation for lost circulation control: Dataset and Analysis

Lost circulation is a recurring problem during well drilling. This work proposed a new gel formulation, and optimizes its composition using a fractional design of experiments. The gel was analyzed using rheology and nuclear magnetic resonance (NMR). The responses were the maximum elastic modulus (G'max), plateau G', gelation time according to the Hill5 model, gel stability (%), gelation time obtained from NMR and the presence of syneresis, also obtained from NMR. Models were created considering the main effects and first order interactions, and showed a very high coefficient of determination, over 0.95. A more detailed ANOVA can be found in the paper. In general, pH and amount of acrylic acid are the most significant effects, but the amount of ammonium persulfate (APS), chromium (III) salt and carboxymethylcellulose are also relevant. The rheological properties match or are higher than those from the literature, showing this formulation is a good candidate for lost circulation control. A set of optimal gel compositions can be obtained from the data, depending on the desired characteristics of the gel, such as its gelation time and viscoelastic properties. These can be used for further tests under high temperatures and pressures, such as a breakthrough pressure test.

钻井作业中，井漏是一类频发难题。本研究提出了一种新型凝胶配方，并采用部分因子实验设计对其组分进行优化。通过流变学方法与核磁共振（nuclear magnetic resonance, NMR）对该凝胶展开分析，本次实验的响应指标涵盖最大弹性模量（G'max）、平台储能模量（G'）、基于Hill5模型推导的胶凝时间、凝胶稳定性（百分比）、通过NMR测得的胶凝时间，以及同样通过NMR表征得到的脱水收缩现象。研究构建了兼顾主效应与一阶交互效应的预测模型，其决定系数高达0.95以上，更为详尽的方差分析（analysis of variance, ANOVA）结果可参见原文。总体而言，pH值与丙烯酸用量是影响最为显著的因素，但过硫酸铵（ammonium persulfate, APS）、三价铬盐以及羧甲基纤维素的用量同样具有重要影响。该凝胶的流变学性能与现有文献报道结果相当甚至更优，表明此配方可作为井漏防控的优质候选材料。基于本实验数据，可根据凝胶的预期性能指标（如胶凝时间与黏弹性能）筛选得到一系列最优凝胶组分配比，上述最优配比可用于后续高温高压环境下的测试实验，例如突破压力测试。