The natural capacity of dense reservoir is very low, only by fracturing can it be developed efficiently, but after-pressure evaluation has always been a world problem. single stage after-pressure stop pump pressure analysis can be used to evaluate the crack half-length of each stage and guide the fracturing scheme optimization, to improve the accuracy of the capacity evaluation after fracturing. At present, the micro-seismic and potential measurement methods are not only difficult to construct, high cost and low accuracy, but also cannot obtain the core parameters of capacity calculation, such as fracture diversion capacity and permeability. Therefore, exploring economical and effective fracturing evaluation method is the key to the efficient development of dense oil and gas reservoirs.

Pre-processing of stop pump pressure test data

Bottom-hole pressure conversion for variable density and flow

During fracturing, different types of fracturing fluid are injected and sand adding is also required. The viscosity, density and so on physical parameters of different types of fluid will produce complex flow in the wellbore，so that the calculation method of converting the wellhead pressure to the bottom hole pressure is very complicated. According to the principles of mechanical mass conservation, momentum conservation and energy conservation in wellbore, this project establishes the vertical pipe flow equation of wellbore considering variable density and fluid physical property, and adopts Longer-Kut method to solve the equation, so as to ensure the accuracy of the wellhead pressure converted to the bottom hole pressure, and to provide guarantee for the correct interpretation and analysis of the stop pump pressure.

Filtering elimination of water hammer pressure after stop pump

The pressure oscillation produced by stopping pump, that is, water hammer effect, has a great influence on the pressure and derivative curve in the early stage. In order to better analyze and explain the stop pump pressure data, it is necessary to process the pressure data after stop pump fracture by filtering.

Analysis of stop pump pressure data software

The bottom-hole pressure solution of multiple stage fracture horizontal well in Laplace space and physical space

Multi-stage fracturing horizontal well stop pump data analysis plate drawing

According to the number of different fractures, different fracture length and different permeability, different pressure and derivative double logarithmic plate are obtained. Because of the many parameters in horizontal well fracturing, we propose to manage the graph plate according to the importance of curve parameters, size order and so on, which is beneficial to improve the speed of curve simulation.

Stop pump data analysis for each layer of pressure data

Through the analysis, we can obtain: the half length of each fracture, the diversion capacity, and the parameters such as permeability, area and average pressure in the SRV area.

Interpretation and evaluation of report preparation

Based on the test and analysis, combine the drainage reality, the influence of different drainage methods on the seepage capacity of gas-water reservoir two-phase flow is studied. At the same time, the stress state is evaluated by using the pressure recovery well test results.