Research Of Wax Precipition Effect On Oilwell Productivity In High-wax Oil Development

In China, there are many high wax reserviors. With the exploration of the reservior, the formation pressure and temperature will change. Thus, the wax in oil and gas will separate and deposit in the rock and may even block the reservoir pore and lower the producitivity. The organic solid precipitation in oil/gas development has always affected the daily production of the oilfield. It will not only block the pipeline of oil and gathering system, but will also cause different damages to reservoir multipore medium, including blocking reservoir pore, lowering porosity and permeability, changing the wettability and affecting the improvement of recovery rate. The organic solid precipition test study and theorectical study will help us to improve the predictability of its precipitation in oil/gas development and minimize its damage to the largest extent.Based on the previous research result, a series of research has been made in this thesis, including wax deposition mechanism in the reservoir, wax solubility model, the mathematical model of the reservoir flow including solid phase wax, numerical model and numerical solution method etc. A mathematical model of wax precipitation was established and an applied simulation software was developed to operate simulation research of the wax influence on singile well productivity. The details are as follows:(1) Compare and analyze four main types of wax precipitation mechanism and study various influences on wax precipitation, including pressure, temperature etc.(2) From regular solution theory, the thesis established the normal solution theoretical thermodynamic model of wax precipitation with reference to solid-liquid phase balance thermodynamic and studied wax precipitation under different pressure and temperature. (3) Use the capillary cluster method to deduct the relationship model between wax precipitation and permeability decline that can be used to calculate the permeability decline degree in different wax precipitation.(4) Establish the single well wax precipitation model in oil/water biphase condition, give out the computation method of mathematical model and compile the computation program.(5) Use the above theoretical method and program to actual oilfield modeling and analyze the influence of wax precipitation on oil well productivity quantitatively and the stimulation effect of oil well heating.