Multi-Stage Fractured Tight Gas Horizontal Well Test Data Interpretation Study
Authors: Yuan Dongrui , Sun Hu , Li Yanchun , Zhang Mian , Chi Xiaoming , He Xiangchu 
Published: March 2015

Abstract
In recent years, horizontal well technologies are becoming the primary developing means for tight gas reservoirs. In Changqing oil field, 70% -80% of natural gas is tight gas, so multi-stage fracturing is becoming one of the main well stimulation technologies for every gas well. In this area, single well fracturing scale is up to 21 stages, Monolayer maximum plus the amount of sand 127.4m3, and ceramsite into the well is about 1274m3.. In order to evaluate post-frac properties of the horizontal wells, deliverability test and transient pressure test have been conducted for some wells. Fractured Multi-Stage horizontal well test interpretation technology is still at the exploratory stage, For heterogeneity tight gas reservoirs, there are great differences between real formation properties and results interpreted by the conventional horizontal well test interpretation model and multi-stage horizontal wells interpretation model that is being developed currently. In this paper, analytical well test and numerical well test methods are respectively used to analyze the same multi-stage horizontal well test data for acquiring post-frac fracture and reservoir parameters and evaluate fracturing results. From the analysis results, the fracture parameters sensitivity is poor during curve fitting and the results have great limitations if data interpreted by multi-stage horizontal wells analytical well test model, while accurate fracture and reservoir parameters can be obtained if test data is interpreted by the numerical well test model because it just can compensate for the shortcoming of analytical well test.

Introduction
Horizontal well technologies have become one of the important technologies for tight reservoir development. In recent years, horizontal well technologies are more widely applied in the Changqing gas field, Large-scale fracturing as the primary means of horizontal wells stimulation is also applied widely because yield increase is very obvious after stimulation. Max post-frac production of horizontal well is up to 454.7×104 m3, which is 3 times of the adjacent vertical well production. In order to obtain accurate formation dynamic parameters and gas reservoir production capacity and stable productivity of horizontal wells, the demand of horizontal well testing technologies are also growing. Compared with vertical wells and horizontal wells not fractured, near wellbore flow characteristics of the fractured horizontal well have been changed because of artificial fractures, so the pressure dynamic characteristics are quite different. Fractured horizontal well test interpretation is still in the exploration and development stage, while Numerical well test need not be limited to the analysis model, a geological model can be established based on the actual formation geometry and horizontal wells trajectory, and the each fracture parameters can be established according to the hydraulic fracturing scale, which has great advantages in multi-fractured horizontal well test interpretation.
Following is a staged fracturing horizontal well testing data, the analytic testing method (heterogeneous reservoirs horizontal wells and multi-stage fractured horizontal wells model) and numerical well test interpretation method is respectively used for evaluation. From the interpretation results, numerical well test is the most effective method for multi-fractured horizontal well testing data.