Abstract
Budged estimation for a given drilling project is part of the dutties assigned to drilling engineers. The simplest way to make those estimations is using average costs based on previous wells, which works well to a certain degree.
Average time and costs sometimes include troubles experienced in wells that could increase the estimation.
This paper presents a simple procedure to make more realistic estimations based on the actual well design of the wells to be drilled and the information compiled from wells already drilled. The Tapir field in Andespetroleum was used to prove the effectiveness of this approach.
Time estimation for drilling operations is made from the information collected in a database, which considered the previous wells drilled in the Tapir field. Wells were classified by their directional profiles, their displacement, their direction and maximum inclination.
The collected information also included a record of average ROPs for each section of the wells, time spent for each trip, and also the time spent in other operations such as open hole logging, casing running, cementing, wellhead / BOP installation, etc.
Once the conceptual design of the new well is ready, wells with similar profile are searched into the database trying to find one well with the closest possible profile respect to the well being planned. This well is called the pattern well. Then, a simple spreadsheet is used to quickly estimate the time for drilling operations using the pattern well as reference.
Oportunities for time optimization are derived from the lessons learnt from each well.
On the other hand, the cost estimation uses a very simple spreadsheet that collects all the associated services involved in drilling a well. It is important to point out the advantage of having services that are paid using a lump sum (drilling fluids, directional services, cementing, etc) which provides a very simple way to estimate costs with a good degree of accuracy. The lump sum contract model for almost each service was adopted after several years of experience in the area that resulted in a good knowledge of the risks and operations associated.
An example of how to use this simple approach is showed and a comparison for planned versus real time and costs are also presented.
