Well Logging Interpretation Method for Oil-Water Two Phase Flow

Abstract

The production profile can be obtained with a continuous flow meter and a gradiomanometer. Slip and other factors in the vertical string for two phase (oil-water) flow, affect the data and make it very difficult to interpret. To solve this problem, studies were made in a simulation well of the relationship between the rotary speed of the spinner and the water holdup, and the ratio of the apparent velocity to the average fluid velocity and water holdup. Four relationship charts and interpretation programs were developed. A total model of the simulating experiment was built, which can interpret multiple zone oil/water production rates to draw their profile map, and quantitatively interpret oil bubbles moving upward, and interpret the reverse rotation of the spinner in the vertical string. The data obtained from 20 wells show that the method has high resolution so that low producing layers can be detected and quantitatively interpreted. Also, intra-formational interpretations for thick formations can be made. In conjunction with the water intake profile of the surrounding injection well, a plot of water-injection versus oil-production can also be drawn. Introduction Daqing Oilfield has entered into the stage of high water cut. To maintain high and stable production rate, the reservoir producing situation must be known. A satisfactory fluid production profile can be obtained with a continuous flow meter and a gradiomanometer under the conditions of the two phase (oil-water) flow. Compared with inflatable and station measurements, continuous measurement has many advantages. The upper limit for flow rate is over 1000 m3/d. Logging speed is high and repeat runs can be made. The log data are reliable and can reflect the intra-formational changes of a thick formation. However, there is some slip between oil and water as the two-phase flow moves vertically, so changes in the flow behavior are very complicated and the data interpretation is very difficult. Thus, a study of interpretation methods of two-phase (oil-water) flow was conducted. Test procedure and test result for oil water two phase flow A test for two-phase (oil-water) flow was made in a simulation well. The test media are diesel fuel and water. The tools used in experiment are a spinner flowmeter and a gradiomanometer. Water holdup, Yw, is derived from an average density measured with the gradiomanometer and spinner count, CPS, that is obtained from a continuous flowmeter. Since Daqing oil field has entered into the stage of high water cut, the water holdup in the borehole is generally greater than 50%. Thus, a holdup of more than 40% was selected for the study. Experiments were conducted in two modes, station measurement and continuous measurement. For different water cuts, different flowrates were selected. 27,000 data points were obtained and four charts were generated in this experiment. To determine water cut, Kw, Figure 1 shows the relationship between the spinner count and different water cuts. Figure 2 shows that the relationship between the ratio of the apparent velocity to the average fluid velocity and the water holdup. The velocity measured in the borehole is an apparent velocity, Va, that is the response to the flowrate of the fluid which is covered with spinner. With a measured water holdup, Yw, and apparent velocity, Va, average flowrate Ut1 can be found from Figure 2. Figure 3 shows the relationship of the spinner count (CPS) and the average flow rate, Ut2, under the condition of the continuous measurement. The curved form and changing trend of Figure 3 is generally consistent with similar data obtained with station measurements. The average flowrate obtained from the stationary measurements is Ut3. The spinner response is a negative value when water cut is lower than 40% and flowrate is about 30m3/d. An average fluid velocity Ut can be derived by averaging over Ut1, Ut2, and Ut3. Mathematical model and computerized interpretation program The figures mentioned above were generated with a computer using an empirical formula to fit the experimental data. The computer plotter can automatically plot the apparent velocity regression curve of every station and list the multiple or separate-zone oil and water production profiles. Based on the empirical formula, a mathematical model was build to simplify the multiple element regression as a single-element regression combining various related variables and using them to form new variables. 1. Modeling g(Q, Yw, CPS)=0 the relationships among Q, Yw, Kw, CPS are as follows: