fax 01-972-952-9435. AbstractA majority of industry operators and service companies have adopted directional drilling collision avoidance rules based on stringent controls to prevent surface collisions and consequent human and environmental damage. These rules are found to be severely restrictive for the optimal positioning of wells through deeper reservoir zones where the level of damage from collision can be contained.A new method is proposed that retains existing rules for avoidance of shallow (severe outcome) collisions and provides the option for use of risk based rules in deeper sections of wells where the outcome of a collision would not be as severe. The risk level of collision with respect to any offset well is calculated and then converted to a Risked Clearance Factor, an established standard for evaluating different levels of collision tolerance in wells.Deep intersections have several characteristics which require separate treatment from shallow intersections. They have high convergence angles which minimize the physical space and distance where a collision may occur and they have lower economic risks of a collision relative to the cost of corrective action. This method has been implemented in a field area of rapid prospect planning and development. The rules are designed to be simple and practical in order to reduce planning and drilling cycle time. A matrix of risk elements, specific to the field area is presented for different depths of collision to help to derive the level of tolerable risk. A case history is presented that shows the clear benefit of utilizing the alternate method. Resulting ActionNo action required.

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The well collision separation rule presented in this paper is a culmination of the work and consensus of industry experts from both operators and service companies in the SPE Wellbore Positioning Technical Section (WPTS). This is the second of two papers and complements the first paper SPE 184730 which described the collision avoidance management practices. These practices are fundamental in establishing the environment in which a minimum allowable separation distance (MASD) can be effectively applied. A standardised collision avoidance rule is recommended, complete with parameter values appropriate to the management of health, safety and environment (HSE) risk, and benchmarks for testing it. Together, these should help eliminate the disparate and occasionally contradictory methods in use today. The consequences of an unplanned intersection with an existing well can range from financial loss to a catastrophic blow-out and loss of life. The process of well collision avoidance involves rules that determine the allowable separation and the management of the associated directional planning and surveying activities. The proposed separation rule is based on the pedal curve method and is expressed as a separation factor, a dimensionless number expressed as a ratio of an adjusted centre to centre distance between wells divided by a function of the relative positional uncertainty between the two. The recommended values for the rule's parameters are based on a comparison of various industry models and experience. The relationships between key concepts such as separation factor, MASD and allowable deviation from the plan (ADP) are discussed, together with their interpretation and application. The dependency on the error distributions of the survey instrument performance models used to establish the tolerance lines is also discussed. The consequences of implementing a standardised separation rule across the industry are far reaching. It influences slot separations, trajectories, drilling practices, surveying programme and well shut-in. It is shown how the MASD can be related to a probability of crossing and being on the far side, or wrong side of an offset well. It is shown why this qualification is required for safe drilling practices to be preserved. Examples are presented to help the reader validate the calculations and software necessary to perform them. The limitations of the methods are explained and areas are highlighted for further work. The methods outlined here, taken together with SPE 184730, if implemented will improve efficiency in planning and executing wells and promote industry focus on the associated collision risks when drilling. The WPTS is also supporting the current development of the API Recommended Practices for Wellbore Positioning (RP78). Mathematical derivations or references are shown for all the calculations presented in the paper.

Summary The well-collision-avoidance management and principles presented in this paper are a culmination of the work and consensus of industry experts from both operators and service companies in the SPE Wellbore Positioning Technical Section (WPTS). This is not a new subject, but current guidance is disparate, company-specific, and occasionally contradictory. As a result, the guidance can be difficult to understand and implement. A further aim is to drive the standardization of the well-collision-avoidance rules, process, and nomenclature throughout the industry. Standardization improves efficiency and reduces implementation errors. The consequences of an unplanned intersection with an existing well can range from financial loss to a catastrophic blowout and loss of life. The process of well-collision avoidance involves rules that determine the allowable well separation, the management of the associated directional planning and surveying activities, and assurance and verification. The adoption of a specific minimum-allowable separation rule, no matter how conservative, does not ensure an acceptably low probability of collision. Many other factors contribute, such as the level of compliance by office and rig personnel with collision-avoidance procedures, and the completeness and correctness of the directional database. All these factors are connected. The material is split into eight sections, each dealing with a critical element in the collision-avoidance process. Examples are presented to highlight a good-implementation practice. This aligned approach will dispel some of the current confusion in the industry concerning well-collision avoidance; will improve efficiency when planning and executing wells; and will build industry focus on the associated collision risks when drilling. The WPTS is also supporting the current development of API RP 78 (not yet issued). This is the first of two papers. The second paper (Sawaryn et al. 2018) covers the minimum-allowable separation rule and its application, assurance, and verification.

Summary The well-collision-avoidance separation rule presented in this paper is a culmination of the work and consensus of industry experts from both operators and service companies in the SPE Wellbore Positioning Technical Section (WPTS). This is the second of two papers and complements the first paper, SPE-184730-PA (Sawaryn et al. 2018), which described the collision-avoidance management practices. These practices are fundamental in establishing the environment in which a minimum allowable separation distance (MASD) (in m) between two adjacent wells can be effectively applied. A standardized collision-avoidance rule is recommended, complete with parameter values appropriate to the management of health, safety, and environment (HSE) risk, and benchmarks for testing it. Together, these should help eliminate the disparate and occasionally contradictory methods currently in use. The consequences of an unplanned intersection with an existing well can range from financial loss to a catastrophic blowout and loss of life. The process of well-collision avoidance involves rules that determine the allowable separation and the management of the associated directional planning and surveying activities. The proposed separation rule is dependent on the pedal-curve method and is expressed as a separation factor, a dimensionless number that is an adjusted center-to-center distance between wells divided by a function of the relative positional uncertainty between the two. The recommended values for the rule's parameters result from a comparison of various industry models and experience. The relationships between key concepts such as the MASD and allowable deviation from the plan (ADP) are discussed, together with their interpretation and application. The dependency on the error distributions of the survey-instrument performance models used to establish the tolerance lines is also discussed. The consequences of implementing a standardized separation rule across the industry are far-reaching. This affects slot separations, trajectories, drilling practices, surveying program, and well shut-in. We show how the MASD can be related to a probability of crossing and being in the unacceptable-risk region of an offset well. We show why this qualification is required for safe drilling practices to be preserved. Examples are presented in Appendices A through D to help the reader validate the calculations and the directional-drilling software necessary to perform them. The geometrical and statistical limitations of the methods are explained and areas are highlighted for further work. The methods outlined here, taken together with SPE-184730-MS, will improve efficiency in planning and executing wells and promote industry focus on the associated collision risks during drilling. The WPTS also supports the current development of API RP 78, Recommended Practices for Wellbore Positioning. Mathematical derivations or references are shown for all the calculations presented in the paper.