An Operator-Oriented Data Acquisition System For Coiled-Tubing Units
Authors: Eriken V.I. , Foster J.C. 
Published: October 2008

When equipped with certain electronic hardware a coil tubing unit (CTU) can acquire powerful capabilities. Among these are automatic monitoring of equipment and process variables, and on-line computational support to the CTU operator. A data acquisition system (DAS) that vastly expands CTU capabilities has been developed. The DAS digitally displays live sensor data. L continually stores job data to disk while making a hardcopy plot Of key variables. It constantly computes and displays coiI tubing stresses and pressure collapse point to give the W operator a better idea of his safety margin. It ho gathers data for tubing management and for prediction of useful life. Analysis of data from the AS, tubing fatigue tests, and theoretical studies yields useful insights. These in turn guide efforts med at continuous improvement in the quality of CTU-delivered services.

INTRODUCTION

An on-going trend in electronics is the unrelenting cramming of greater computing power and higher data storage capacity in smaller space at lower cost. This arises from higher levels of circuit integration in turn leading to increased miniaturization of electronic devices. The trend progressed far enough that it became feasible to implement the laptop PC. It also has made possible sensors in which miniaturized electronic signal conditioning circuitry is embedded internally. Various devices that take advantage of the trend alluded to above are now available. These have now made it practicaI to design and assemble a data acquisition system (DAS) that brings unprecedented cost- and space-effective on-line computation resources aboard a coil tubing unit (CTU). In turn, this makes it possible to greatly enhance a coil tubing unit with an integrated set of capabilities. A simple example of such an added capability is the ability to digitally display for the CTU operator live sensor and transducer data instantaneously in engineering units.

Even more helpfully, stresses on coil tubing can generaJ1y be calculated in red time and displayed to the CTU operator in relation to some predetermine safety margin. Similarly, data needed for coil tubing management and tubing life prediction can be gathered and stored automatically with no need for operator intervention. Some design factors and tradeoffs to consider when designing a coil tubing unit data acquisition system are touched on and briefly discussed.

RATIONALE FOR OPERATOR ORIENTATION

Various applications of coil tubing require the monitoring of certain key parameters to assure proper execution and safe completion of the job. Pre-job planning has typically been done on an office PC away from the job site. This usually requires that assumptions be made about some of the features of the well or of certain characteristics of the process being simulated. Many times when subsequently executing a job the operator of a coil tubing unit encounters a situation where some assumptions made during the job planning phase have turned out to be substantially incorrect. This may be due to a number of reasons: incorrect or incomplete data was supplied by the well owner, or unforeseen events occur during the job that require a change of approach or reassessment of assumed parameter values than those used in pre-job calculations.