Polymer flooding has been extensively applied to oilfields as an effective method for EOR, but along with injected time growing, some wells' bottomhole pressure rose up and oil production dropped, and the formation pressure rose while the reservoir was blocked, and water production of the other wells increased while the reservoir was channeled. An analytical method based on well test analysis is developed to incorporate well test pressure data with production data to verify whether the polymer flooding plays a role in displacing oil into wellbores.
Based on the non-Newton polymer well test analysis models to consider the polymer non-Newton effect, this paper employs two well groups located in Shuanghe polymer flooding pilot unit of Henan Oilfield by using the dynamic performance analysis approach in which the well test information is combined with the production data to judge the blocking and channeling. First qualitative analysis is performed to compare different period pressure history curves of the different period pressure test data by drawing Cartesian coordinate charts and log-log diagnosis charts of pressure change and its derivative of all the well test data with production history data for a well. Secondly we interpret all the well test data from the two well groups with 6 periods' well test data to obtain the formation parameters by using non-Newton fluid well test analysis software.
Blocking and channeling could be judged qualitatively and quantitatively by correlating different period pressure trend and production data trend charts and parameters from the different period well test interpretation. For blockage, oil production flow rate dropped, the formation pressure rose and wellbore skin factors increased for production wells, and reservoir permeability decreased. For channeling effects, both production flow rate and water cut increased, but the formation pressure almost did not change and reservoir permeability did not change. To recognize the geological characteristics and production condition of the two well groups based on the above ideology, Non-Newton composite models with two zones is chosen to analyze the tested wells to acquire the skin factor, internal and external zone flow capacity, internal area radius, formation pressure. Since skin factor and formation pressure increase, both internal and external area zone flow capacity reduce, and internal area radius becomes smaller. It is concluded that the areas around the tested wells have been blocked.
Most innovative aspect of the methodology developed in this paper to judge blocking and channeling effects of polymer flood reservoir in a systematic fashion is by contrasting different periods of tested pressure change trend, flow rate change trend and production water cut change trend with the parameters obtained by non-Newton fluid well test analysis to get a more direct solution of resultant lower uncertainty.