Coiled-Tubing Wiper Trip Hole Cleaning in Highly Deviated Wellbores

Abstract

Abstract Wiper trips are the current field practice to clean the hole for coiled tubing drilling or sand clean out operations. A wiper trip can be defined as the movement of the end of the coiled tubing in and out of the hole, a certain distance. In order to clean the solids out of the wellbore, a proper wiper trip speed should be selected based on the operational conditions. There is no previously published information related to the selection of the wiper trip speed. In this study, numerous laboratory tests were conducted to investigate wiper trip hole cleaning and how the hole cleaning efficiency is influenced by solids transport parameters such as;Nozzle Type,particle size,fluid type,deviation angle,multi-phase flow effect. The results indicate the following:Compared with stationary circulation hole cleaning, the use of the wiper trip produces a more efficient clean out.For a given operational condition, there is an optimum wiper trip speed at which the solids can be completely removed.Nozzles with a correctly selected jet arrangement yield a higher optimum wiper trip speed and provide a more efficient clean out.The hole cleaning efficiency is dependent on the deviation angle, fluid type, particle size, and nozzle type. Correlation's have been developed that predict the optimum wiper trip speed and the quantity of solids removed from and remaining in the wellbore for given operating conditions. The wiper trip provides an advantage for hole cleaning and can be modeled to provide efficient operations. Introduction Solids transport and wellbore cleanouts can be very effective using Coiled Tubing techniques, if one has the knowledge and understanding of how the various parameters interact with one another. Poor transport can have a negative effect on the wellbore whether it is for coiled tubing drilling or cleanouts, which may cause sand bridging and as a result getting the coiled tubing stuck. Coiled Tubing can be a very cost-effective technology when the overall process is well designed and executed. The highly deviated/horizontal well has placed a premium on having a reliable body of knowledge about solids transport in single and multi-phase conditions. In our previous studies1–2, a comprehensive experimental test of solids’ transport for the stationary circulation was conducted, which included the effect of liquid/gas volume flow rate ratio, ROP, deviation angle, circulation fluid properties, particle size, fluid rheology, and pipe eccentricity on solids transport. Based on the test results the data was analyzed, correlation's were developed, and a computer program was developed. In this study, the wiper trip hole cleaning effectiveness was investigated with various solids transport parameters such as, deviation angle, fluid type, particle size, and nozzle type. Based on these test results, an existing computer program was modified and adjusted to include these additional parameters and their effect on wiper trip hole cleaning. Experimental Setup The flow loop shown in Figure 1 was used for this project. It was developed in a previous study1–2. The flow loop has been designed to simulate a wellbore in full scale. This flow loop consists of a 20ft long transparent lexan pipe with a 5-inch inner diameter to simulate the open hole and a 1–1/2" inch steel inner pipe to simulate coiled tubing. The flowloop was modified and hydraulic rams were installed to enable movement of the tubing (see figure 2). The inner pipe can be positioned and moved in and out of the lexan to simulate a wiper trip. The loop is mounted on a rigid guide rail and can be inclined at any angle in the range of 0°–90° from vertical. When the coiled tubing is in the test section, circulating the sand into the test section and build an initial sand bed with an uniform height cross the whole test section. Then pull the coil out of the test section with a preset speed.