Depth conversion is an important step of the seismic reflection method, which converts the acoustic wave travel time to actual depth, based on the acoustic velocity of subsurface medium (sediments, rocks, water).

Depth conversion integrates several sources of information about the suburface velocity to derive a three dimensional

Three-dimensional space

Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...

 velocity model:

• "Well tops", i.e., depth of geological layers encountered in oil
  Petroleum
  Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
  
   and gas
  Gas
  Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
  
   well
  Oil well
  An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
  
  s
• Velocity
  Velocity
  In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
  
   measurements made in oil
  Petroleum
  Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
  
   and gas
  Gas
  Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
  
   well
  Oil well
  An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
  
  s
• Empirical knowledge about the velocities of the rocks in the area investigated
• Root Mean Square
  Root mean square
  In mathematics, the root mean square , also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids...
  
   (RMS) stacking velocities which are derived from the processing of the seismic reflection data

This conversion permits to produce depth and thickness maps of subsurface layers interpreted on seismic reflection data. These maps are crucial in hydrocarbon exploration because they permit the volumetric evaluation of gas or oil in place. In the example subsurface map presented below, depth increases from red to blue. The highest zone in red is an oilfield at approximately 3000 m below sea level.

Software for depth conversion

• Seismic Unix
  Seismic Unix
  Seismic Unix is an open source seismic utilities package supported by the Center for Wave Phenomena at the Colorado School of Mines .- History :...
  
   - open source seismic software
• VelocityManager - Commercial software minimising uncertainty.
• DUG Insight - Commercial software by DownUnder GeoSolutions
• Promax - Commercial software by Halliburton
• TDQ - Commercial software by Halliburton
• VelPAK - Commercial software from Seismic Micro-Technologies
• Petrel
  Petrel (reservoir software)
  Petrel is a Schlumberger owned Windows PC software application intended to aggregate oil reservoir data from multiple sources. It allows the user to interpret seismic data, perform well correlation, build reservoir models suitable for simulation, submit and visualize simulation results, calculate...
  
  - Commercial software from Schlumberger

External links

• Depth conversion definition in the Oilfield Glossary
• True depth conversion: more than a pretty picture - presentation of different methods for depth conversion
• A pdf document presenting different variations of the V₀-K depth conversion method