Accurate Surveying: An Operator's Point of View (1988)

Accurate Surveying: An Operator's Point of View J.I. de Lange; J.I. de Lange Koninklijke/Shell E and P Laboratorium Search for other works by this author on: This Site Google Scholar G.D. Nijen Twilhaar; G.D. Nijen Twilhaar Koninklijke/Shell E and P Laboratorium Search for other works by this author on: This Site Google Scholar J.J. Pelgrom J.J. Pelgrom Koninklijke/Shell E and P Laboratorium Search for other works by this author on: This Site Google Scholar Paper presented at the IADC/SPE Drilling Conference, Dallas, Texas, February 1988. Paper Number: SPE-17213-MS https://doi.org/10.2118/17213-MS Published: February 28 1988 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation de Lange, J.I., Twilhaar, G.D. Nijen, and J.J. Pelgrom. "Accurate Surveying: An Operator's Point of View." Paper presented at the IADC/SPE Drilling Conference, Dallas, Texas, February 1988. doi: https://doi.org/10.2118/17213-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE/IADC Drilling Conference and Exhibition Search Advanced Search AbstractThe achieved survey accuracy from the modern survey tools can be quantified by analysis of run data. Knowledge of the achieved accuracy, often better than the beforehand estimated accuracy, could result in reduced surveying cost and less rig time spent on surveying. Survey companies are urged to improve QA/QC and to provide the operator with 'simple' yardsticks with which to judge actual performance.IntroductionSurvey accuracies of conventional compass and gyro tools have been studied extensively in the past. In recent years new survey tools, solid-state magnetic and rate-integrating north-seeking gyro tools, have been developed by the survey industry. These new tools are intended to improve the accuracy of monitoring the downhole wellbore position while drilling and after completion of wells.In spite of improvements in surveying techniques and tools, it is still necessary to run different types of survey tools to confirm the downhole wellbore position. Confidence is gained in the survey results when the downhole wellbore positions resulting from these different surveys coincide or are very close. Normally this is not the case and one has to be satisfied with a result in which the 'calculated, ellipses of uncertainty for the two or more surveys overlap. This indicates that the actual downhole wellbore position is somewhere in the overlapping uncertainty area. A 'final' downhole wellbore position can then subjectively be selected or a weighing method can be used that takes into account the results of all surveys. The latter method has the disadvantage that bad surveys are also taken into account.Evaluation of many surveys, feedback from our operating companies and frequent visits to the facilities of and discussions with the experts in the survey and tool manufacturing companies, indicated that an improved knowledge of the achieved accuracy for a particular survey is possible. This should ultimately result for the operator in a reduction of the overall surveying costs by eliminating unnecessary surveys, while still maintaining safe operations.An approach was followed similar to the quality assurance approach recommended for oil field products, reference 1, i.e. study the specifications, error models and QA/QC procedures of survey tools and visit the calibration facilities of the survey companies. In addition, the survey results in our operating companies were studied and multiple runs in the Norway directional reference well, which was designed for difficult surveying conditions, were witnessed and analysed. This approach resulted in the identification of critical survey parameters for checking by our staff in the operating companies on normal survey runs. It also resulted in the identification of companies and tools that produce consistent surveys with a defined quality. This proves to be a powerful approach to cutting costs and not corners. It should be stressed here that a known reduced accuracy does not necessarily have to lead to a rejection of the survey.SURVEY ACCURACY REQUIREMENTSBefore embarking on the analysis of survey results, it is useful to consider the survey accuracy requirements. These requirements should be used in the planning stage of any well to establish the survey program. In other words, when the results of a survey are not critical, then one should not spend a vast amount of money on accurate surveying techniques.P. 325^ Keywords: survey company, strength, spe 17213, operator, spe drilling conference, trajectory design, knowledge, accuracy, position uncertainty, declination Subjects: Well Planning, Drilling Operations, Trajectory design This content is only available via PDF. 1988. IADC/SPE Drilling Conference You can access this article if you purchase or spend a download.