Review of Hole Cleaning in Complex Structural Wells

Abstract

Abstract:Complex structural wells are widely used in the development of marine oilfield, old oilfield and low permeable oilfield. However, poor hole cleaning is often occurred in the highly-deviated sections and horizontal sections of the complex structural wells, which affects rate of penetration and downhole safety.The methods to study cuttings transport can be normally divided into four types: 1) experimental observations, 2) CFD simulations, 3) theoretical correlations and models and 4) field tests. Experimental observations and CFD simulations are mainly used to analyze the effects of different parameters on hole cleaning and obtain some valuable data. Theoretical models and correlations are mainly applied to calculate cuttings bed height, critical velocity and etc to provide the guidance for the design of hydraulic parameters. The accuracy of the first three types are checked by field tests. In this paper, the effects of flow rate, inclination, mud rheology, drillpipe rotation and other factors on hole cleaning, and some typical correlations and models were briefly reviewed before 2000 years, and some new research findings were detailedly addressed. In addition, CFD simulations also were introduced.Although major improvements have been achieved in the past several decades, building a comprehensive and proven model requires much more experimental researches, CFD simulations, in-depth theoretic studies and field tests due to the complexity of cuttings transport under multi-factor interactions.

Experimental Study of Hole Cleaning Performance of Underbalanced Drilling at Downhole Conditions

“…The critical analysis of the result revealed that although annulus cutting concentration profile decreases as GOR which epitomizes gas volume increases, greater change occurred when GOR was between 0.3 -8.0 for only 0.27m 3 /s and 0.57m 3 /s. The result is in agreement with Leising and Waiton [8] that there exists increase in turbulence by the presence of limited amount of gas and helps the solids in suspense. Thus, the greater increase in hole cleaning performance between GOR 0.3 -8 can be attributed to limited amount of gas volume which primarily increase turbulence and expansion as it near the surface, annular velocity simultaneously increased.…”

“…Sun et al [8] carried out review of research works in hole cleaning in complex structural wells on the effects of flow rate, inclination, mud rheology, drillpipe rotation and other factors on hole cleaning and some correlations and models were developed. The major areas identified as gab for future experimental research study is the use of flow loop that depicts the real cuttings transport under downhole conditions including formation fluid influx, wellbore collapse and the annular temperature.…”

Analysis of Hole Cleaning for a Vertical Well

“…The existing problems and characteristics of these correlations and models were summarized by [15]. Theoretical models and correlations mainly applied to calculate cuttings bed height, critical velocity to provide the guidance for the design of hydraulic parameters and the effects of flow rate, inclination, mud rheology, drill pipe rotation and other factors on hole cleaning, in addition, CFD simulations was applied [16]. In real time drilling, mud properties in any type of wells rather are complex with numerous parameters.…”