--> --> A New Method to Match Trajectories of a Horizontal Well in Time Domain and in Depth in Ancient Buried Hill presented by Jinlong Wu

2018 AAPG International Conference and Exhibition

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A New Method to Match Trajectories of a Horizontal Well in Time Domain and in Depth in Ancient Buried Hill presented by Jinlong Wu

Abstract

In the complex buried hill reservoir, since the current professional seismic software can not realize variable time-depth relationship in horizontal direction, which leads to the error of the trajectory position of the horizontal well in time domain, therefore the well trajectory in time domain is not matched with that in depth. Aiming at this difficult problem, in our reservoir characterization study, from the study of theoretical form of the horizontal well trajectories in time and in depth domain under different buried hill top form, combining the actual situation of JZS Oilfield, a new pseudo time-depth relationship (MD&TWT) based on a certain number of virtual wells is put forward, therefore the problem is solved well. Specific methods and processes are as follows: Firstly, the seismic calibration of the buried hill horizontal well is carried out by using the time-depth relationship (TVD&TWT) of the neighboring exploratory well, then a time-depth relationship (TVD&TWT) of the horizontal well can be established, the TVD&TWT relationship can be converted to MD&TWT format, and the data of buried hill segment need to be deleted. Secondly, for the trajectory of the buried hill segment, we need select one point every 30m to 60m by measure depth in the trajectory, read the plane coordinates (X,Y) of the point, design a virtual vertical well through this point, read the time and depth value of the buried hill top surface of the virtual well in time and in depth domain respectively, calculate the time value of the intersection between the virtual well and the horizontal well according to the interval velocity of the buried hill, and establish pseudo time-depth relationship (MDi, TWTi) of the horizontal segment. Finally, we can establish the time-depth relationship of the whole well by merging the horizontal segment in upper directional well segment. Through this study, we can obtain the accurate trajectory position of the horizontal well in time domain and it provides a basis for accurate geological modeling based on 3D seismic attributes data. The real reservoir performance of JZS buried oilfield in Bohai Bay in China has proved that the 3D geological model based on the new time-depth relationship (MD&TWT) of the horizontal wells is closer to the actual reservoir.