Wunan Oilfield Increase Well Production Technology Research And Application

As the technology of exploration and exploitation becomes more sophisticated, the production from low permeable reservoir takes a bigger and bigger share in the total production. In the year of2000, two-thirds of the identified reserve is low permeable reserve. But low permeable reservoir is of lithologic layers, rather than of tectonic layers, leading to its difficult development. So, how to effectively exploit low permeable reservoir is significant in maintaining the steady operation of PetroChina.Wunan Oil Field is typical of low permeable reservoirs in Caidamu Basin, which has an identified geologic reserve of2.78813million tons, and a recoverable reserve of0.27946million tons. But it is seriously segmented by defaults, and has the following disadvantages such as a diversity of layer features, a tense hydrophilicity, smaller diameter of pore throat, a low permeability, a low saturation pressure in layer, and a trend of a mixing flow of two phases of oil and gas. In addition, fracturing can easily induce water locking and sensitive reaction of rock. So, all the above disadvantages result in the hardship of fracturing and injection in a large scale, leading to low production of a single well.In order to effectively exploit the field, the following tasks have been finished. Reasons for constraining the stimulating measures are found out by further evaluation of layers features in combination with analysis of former fracturing data, and thus the principle of the selection of a well and a layer to be stimulated is laid out. Fracturing liquid system to prevent water locking is optimized, and so is the technology of nitrogen back drawing before fracturing. Technology to prevent fracture deforming, serious fluid filtrating, and early sand plugging is applied successfully. The wells pattern and fracturing parameters in Zone Wu-101are optimized by analogous calculation on the20kinds of combination of4patterns of wells and5well spaces. Fracturing parameters in Zone Wu-5are optimized by a software of FracproPT. Feasibility of increasing injection is studied, and parameters of fracturing and acidizing for injection wells are optimized, with on site experiments on increasing injection for6wells to get an injection increase of21.33cubic meter per day, and with fracturing of3injectors and20producers that have a successful rate of86.59%and a effective rate of85.7%. Related data show that the ratio of input to output is1:3.22, reaching the goal of economic exploitation of the field. All in all, the achievements described in this paper are a guideline to exploiting low permeable reservoirs.