活性原油在非均质储层中的自适应控水增油机理

Increasing oil production and controlling water cut, as well as improving oil recovery is always an important goal during oil production. Water plugging is an important measure to improve the sweeping coefficient of water and enhance oil recovery. For high water cut oil well with indefinite layer of water production or oil/water in the same layer，selective chemical water plugging technology can solve the problem above well. Active crude oil water plugging is one ideal selective water plugging method which can plug water channel selectively and doesn’t damage oil channel. When the development of oilfield entering into high water cut stage, the problem of water production in oil well is becoming more prominent and the effect of blocking water by active crude oil is decreasing gradually. The effects are very different from one oilfield to another. So, it is necessary to clarify the action mechanism of plugging water by active crude oil and find out the main reasons which result in the effect of blocking water decreasing..Based on measurement of emulsifying properties, though visual micro test, the force status, flowing, deforming and distribution of the emulsion droplets in rock cores will be studied, and the effect on plugging flow channel by active crude oil will be revealed. This topic studies on the influence of blocking water and increasing oil production in these aspects: the properties of crude oil and water, the type and concentration of emulsifiers and additives, remaining oil distribution, fluid properties, oil reservoir physical property, injection parameters. We will find out the relationship between different factors and effects, make clear the micro-mechanism of controlling water cut and increasing oil production, determine the principles of adjusting formulae and optimum dosage of chemicals in a single well, and eventually put forward a set of theory and method of blocking water by active crude oil in high water cut stage.

增油控水和提高原油采收率始终是油田生产的重要目标，堵水是增加水的波及系数，提高采收率的重要手段。对于出水层位不明确及油水同层的非均质储层的中高含水油井，活性原油堵水是一种自动封堵水流通道、对油层无损害的理想的选择性堵水方法。但随着油田开发逐步进入到高含水期，油井出水问题更加突出，实施活性原油堵水效果逐渐下降，不同区块措施效果差别很大，因此有必要明确活性原油堵水的作用机理，找出影响措施效果的主要原因。.本课题将在活性原油的乳化特性研究基础上，通过微观可视化实验，研究乳状液滴在岩石孔道中的受力状况、运动变形规律、分布状态，揭示其对水流通道的选择性封堵作用机制；研究原油及地层水性质、乳化剂分子结构及添加剂的种类和浓度、剩余油分布、地层流体物性、油藏物性、注入参数等对控水增油效果的影响，找出不同因素与措施效果之间的关系，明确活性原油控水增油微观机理，为提高堵水效果提供理论依据。

我国老油田大都已进入高含水期，注水低效无效循环严重。堵水是治理低效无效循环的重要手段。常规堵水剂选择性差，堵水也堵油。活性原油理想的选择性堵水方法，但以往对活性原油堵水的作用机理认识不足，导致措施效果不够理想。.本项目在获得了国家自然科学基金资助后，进展顺利，进一步明确了活性原油在岩石孔道中的乳化特性及其控水增油机理。具体如下：.明确了原油组分与油包水型乳化剂分子结构之间的匹配关系。沥青质和胶的含量越高，原的粘度越高；沥青质和胶质都有助于油包水型乳状液的稳定，且沥青质作用更明显；蒽和菲含量不同致使乳状液粘度差异巨大；乳化剂碳链越长，乳状液粘度越大，稳定性越好；但碳链过长则乳状液粘度反而下降。.明确了活性原油自适应控水增油微观机理。通过理想孔道和岩石孔隙仿真激光刻蚀玻璃模型的堵水实验发现，活性原油优先进入水流大孔道，在油水接触面处原位乳化，随着活性原油向前推进，乳化段逐渐增长，直至停止流动而实现封堵；在孔道的变径、分叉、转弯处较易形成封堵；恢复正向水驱时，注入水会绕流进入到原来水驱未动用的油流孔道，将其中的油驱替出来，实现增油。而进入油流通道的活性原油与孔道中的原油发生混合，不发生乳化，恢复正向注水后，油流通道中的混合油和原来的油被水驱替出来。.随岩石渗透率的增加，乳状液黏度与突破压力先增大后减小；渗透率过低，活性原油注入困难；渗透率过高，剪切扰动不足，乳化效果变差，封堵能力下降。地层水的离子成分对乳状液黏度及封堵强度影响不大。含水率为80%左右时实施活性原油堵水，控水增油效果最好。活性原油注入体积倍数越大，最终采收率越高。随着注入速度的增加，采收率先增大后减小，注入速度存在最佳值；注入速度过慢，剪切扰动作用小，乳化不充分，封堵效果差；注入速度过快，活性原油前缘与孔道中的水乳化增粘快，阻止后续活性原油的进入，封堵不充分；同时，注入速度过快也会导致乳状液剪切破乳，从而降低封堵能力。