Drilling Optimization Software Verified in the North Sea

Abstract

R.K. Bratli*, G. Hareland**, F. Stene*, G.W. Dunsaed* and G. Gjelstad*** Abstract This paper presents the introduction, application and verification of a new drilling optimization approach. During the past decades rate of penetration (ROP) models for all types of drilling bits were developed and verified. The unique software uses these models in a new approach that optimizes the drilling cost on each hole section. The simulation of ROP every foot gives the capability to simulate the effects of all operating conditions, bit design, bit wear and formation properties. All the penetration rate models used can be inverted to solve for rock strength if ROP, operating conditions, lithology percentage and field reported bit wear is known. This imply that if one well has been drilled, and the penetration rates are inverted, a foot by foot strength is obtained, by integrating over each individual bit run until the field reported bit wear matches the calculated. This strength is then used as input for simulation, and it is shown that the drilling cost for one particular 12,25" section can be reduced as much as 45-50 percent by changing bit design and operating conditions. This approach has been verified with North Sea data where the generated rock strength from the 12,25" section has been used as input to simulate the ROP and rotating time. These simulations compare well with the measurements of ROP, made in the two following wellbores drilled in the same field. Simulating ROP using drilling data from a well in a nearby field also gave promising comparisons. Introduction The DRilling OPtimzation Simulator (DROPS) is developed to reduce the cost of future wells based on a Geological Drilling Log (GDL), created from the data collected in a previous well drilled in the same area. The GDL is created using ROP models inverted to calculate rock compressive strength. The simulator has the capability of simulating any combination of operating conditions, bit designs, pull depths, hydraulics, WOB and RPM. The basic idea behind DROPS is to simulate the drilling operation prior to the actual drilling, and to find the optimum cost level. Simulations to verify the software (drill behinds) have been performed using actual field data from the North Sea, provided by Saga Petroleum ASA, well A and B. Data from well C, provided by Statoil, have also been used in the drill behind simulations. The simulated ROP results from the drill behind compares well with the results for actual measured ROP and cumulative rotating time, which are promising for further development and application of the method. Based on the comparison some cost optimizations for future wells in this region have also been performed. The cost reductions obtained indicate potential cost savings of 45-50 percent of total drilling cost per well, compared to the current industry practice in the area. By using this methodology in the planning process the most cost effective drilling program can be obtained.

An Integrated Approach for Drilling Optimization Using Advanced Drilling Optimizer

“…Over the past decades, several methods have been developed to estimate ROP [12]. These models are able to predict ROP from operational parameters and formation characteristics.…”

An Improved Drilling Simulator for Operations, Research and Training

“…Similar simulators were developed in the past [3,4] but almost all had the disadvantage of requiring a large number of parameters to be known a-priori which make the use of the simulators very complex and non-flexible in terms of simulating varying and changing drilling conditions. Another approach that was followed [5,6] was the use of a drilling process model and then using drilling data one could infer information regarding rock drillability allowing for drilling optimization.…”

Drilling Simulation versus Actual Performance in Western Canada

“…This involves trying multiple combinations of drill bits and operating parameters before finally reaching the optimum drilling solution. The use of a drilling simulator has proven that it can significantly improve results with the input of an accurate ARSL [4][5] .…”