The Principles of Geosteering | Geosteering Best Practices

(adsbygoogle = window.adsbygoogle || []).push({}); In this topic, we present a brief list of principles to guide you through planning your GeoSteering project and in actually carrying out your plan. Geosteering Principles Geosteering is primarily a stratigraphic problem, with the goal of exposing the greatest length of horizontal wellbore to the targeted horizon. (If this is NOT the case, then why go to the expense of drilling a horizontal wellbore in the first place?) Therefore, the planning and the drilling of a horizontal well should concentrate PRIMARILY upon the stratigraphy of the target. This is accomplished through focusing upon True Stratigraphic Position rather than True Vertical Depth. When the position of the wellbore is described in reference to a particular stratigraphic marker, it will be much easier for the Geosteering Team to guide the wellbore to its optimum position within the target reservoir. Pre-Drill Planning (adsbygoogle = window.adsbygoogle || []).push({}); Pre-drill planning is a crucial part of geosteering. The primary objective of this stage is to arrive at a thorough understanding of the target reservoir, with emphasis on the structure and stratigraphy. These plans will help ensure that the appropriate tools for analysis will be used and the appropriate personnel resources are prepared to steer the well. Ultimately, if a well is planned correctly, the company’s objectives will be met even if unexpected events occur. Preliminary planning should include two stages: Optimal Planning and Uncertainty Planning. Optimal Plan The Optimal Plan is devised to enable the wellbore to meet all objectives. The plan should be stated in terms of stratigraphic and engineering parameters, and should include: the depth to KOP and its stratigraphic position (which has priority over depth), the depth to target, the stratigraphic description of the target reservoir, the minimum reservoir exposure required to meet objectives, the maximum and minimum inclination, and the expected apparent formation dip. Uncertainty Plan Uncertainty Planning is performed to predict and describe the expected range of variance from the Optimal Plan. Expect uncertainty to occur, both in the mechanics of directional drilling and in the stratigraphy. The Uncertainty Plan should serve as the basis for creating contingency plans that define decision points and set forth the best options before they occur in the drilling phase. For example, the Geosteering Team should plan for sidetrack or bailout points, depending upon whether reservoir exposure objectives are met at the point where a fault cuts the wellbore. If the reservoir exposure objectives are already met and a fault is cut that is too large to steer back into target, then the bailout contingency would dictate that the well be completed at that point. If, on the other hand the reservoir exposure objectives have not been met, then an open hole sidetrack may be the best option for landing the target across the fault. If contingency plans are developed before the well spuds, then valuable time will be saved when such a situation is encountered while drilling. (adsbygoogle = window.adsbygoogle || []).push({}); Active Geosteering (adsbygoogle = window.adsbygoogle || []).push({}); After the well has spud, the process of Active Geosteering will require the GeoSteering Team to constantly think ahead of the bit. The Team should follow these guidelines closely. Prioritize lateral length against reservoir exposure before the well lands in section. Segregate data into that which will be useful for geosteering versus that which will be useful for a full reservoir evaluation. Interpret only the data required to make a steering decision when the well is drilling. Save the rest of the data for later, when time is at less of a premium. Have all data in hand when making decisions! It is usually better to wait until you are sure of the wellbore position, rather than rushing to judgment and making unneeded changes. Communicate with the Directional Driller (who is in the best position to know how the well is drilling). This is a two-way exchange, in which the Team describes expected conditions ahead of the bit, while the Driller reports present conditions: Wellbore conditions BHA performance- How much build up and down? Will he be able to change angle while rotating? Will he be able to change angle using WOB? Will he be able to change angle using ROP? When will torque & drag problems make it impossible to slide? Give the Directional Driller as much flexibility in changing targets as is possible. Communicate targets that are possible, simple, quantitative, and based upon stratigraphy. Realize that every target change may affect the remainder of well.There are consequences for every target change, so weigh the consequences, make a decision, and live with the results. Do not second guess as long as the best decision was made using all of the data. Do NOT over-analyze the data. Though tempting, this practice will generally cause over-reaction and will definitely cause you to loose sleep for no reason. Rest assured that you will be wrong on occasion.When you are, don’t try to ignore it or explain it away.Instead, just correct the mistake as soon as possible to keep from compounding it. Make as few target changes as possible to meet objectives. (adsbygoogle = window.adsbygoogle || []).push({}); Assessment (adsbygoogle = window.adsbygoogle || []).push({}); 1. Planning for sidetracks or bailout points is a part of: A .Optimal PlanB .Uncertainty Plan ✔C .Both (A) and (B) 2. The geosteering team should always prioritize lateral length against reservoir exposure ______. A .before the well is spuddedB .before the well lands in section ✔C .after the well lands in section Recommended for You Case Study Geosteering Geosteering Practices Preparing the Geosteering Plan (adsbygoogle = window.adsbygoogle || []).push({});