There is both oil and water in the oil reservoir, so the oil well not only produces oil, but also produces water. Even if many oil wells do not produce water in the early stage, oil and water will inevitably come out in the later stages of water injection development, and some wells will stop production due to an excessive proportion of water production. Water production from oil wells is a hazard to oil production, so people must do everything possible to control water production. Nowadays, the commonly used oil well water control technologies include the following.
Built partitions to control bottom water. The so-called bottom water means that in a rock formation, oil is stored in the upper part and water is stored in the lower part. For this type of well, generally only a small part of the top of the oil layer is penetrated to control the water production. Once the water content is high, an artificial partition is usually built in the rock layer to separate the oil and water from the upper and lower parts, reducing the water production. The material of the partition is Use more cement.
Illustration of using artificial partitions to block water in the bottom water oil layer
Illustration of water blocking in the packer mechanically blocking the water layer. An oil well often exploits multiple oil layers, possibly because a certain layer mainly produces water. This later leads to high water content in oil wells, affecting oil well production. For this kind of well, we must first find water and determine the water-producing layer, and then use the tool to get stuck in the water-producing layer to prevent water production and allow the oil well to produce more oil.
Chemical method to block the water layer. After identifying the water layer of an oil well, in addition to using downhole tools to block the water layer, chemical methods can also be used to block the water layer. The method is to squeeze into the water layer a chemical substance that can form a certain consolidation strength and no permeability under the formation conditions, block the liquid flow channel, and control the production of water. Commonly used materials include cement, cyanide, etc.
Selective water blocking technology This technology mainly uses materials that only block water but not oil. It is used to block water in oil layers that produce both oil and water. At present, there are many materials with selective water blocking function, such as cationic surfactants, hydrocarbyl halosilane, partially hydrolyzed polyacrylamide, foam, active heavy oil, rosin soap, oil-based cement, etc. Take oil-based cement as an example. It is a suspension of cement in oil. When it is injected into the water-producing layer, it solidifies when it encounters water and blocks the water-producing channel. However, the cement entering the oil-producing layer will not solidify, thereby achieving selective plugging. water purpose.
The above is about water control on oil wells. At present, most oil fields adopt water injection development. When entering the later stage of water injection development, most of the water produced by oil wells comes from the injection water of water injection wells. Therefore, water control on water injection wells is also critical. Due to the differences in fluid channels in each layer of the water injection well, water advances to the oil well at different speeds. If the water advances faster, the oil well will be flooded prematurely. In order to solve this problem, in the water injection well, each layer can be separated by downhole tools, and the water advancement speed of each layer can be artificially controlled to be as close to the same as possible. Another method is to squeeze and inject a substance that can adjust the speed of water into the formation where water advances quickly. This substance thickens under the formation conditions, increases the friction coefficient, and reduces the speed of water; it can also be squeezed into the formation. Materials that can narrow or block formation water channels, causing the injected water to change direction. The technical term for these two methods is water injection well control and flooding. In short, water control can be divided into water control on oil wells and water control in water injection wells. There are many methods and only one purpose, which is to improve the use efficiency of injected water and reduce water production in oil wells.