Experimental Investigation of Cuttings Transport With Oil Based Drilling Fluids

Abstract

Drilling fluids are very complex and are essential for safe and efficient drilling operations. It is vital for the drilling operator to be able to select an appropriate fluid for each individual well, including the decision of using oil-based or water-based fluids or “muds” (OBM or WBM). In this article we present results from a comparative study of three OBM’s which are based on the same fluid system (Versatec). This work is part of a larger investigation where the main objective is to identify and evaluate the difference in the hole cleaning capabilities of OBM’s and WBM’s with similar viscosity as measured by the API/ISO standards. This paper describes an experimental investigation of cuttings transport using flow loop laboratory tests without and with injected cuttings size particles using various industrial oil based fluids with varying density and viscosity. The flow loop includes a 10 meter long test section with 2″ OD free whirling rotating steel drillstring inside a 4″ ID wellbore made of concrete elements positioned inside a steel tubing. Sand particles were injected while circulating the drilling fluid through the test section. Experiments are conducted at atmospheric conditions, but are otherwise designed to represent downhole conditions as closely as possible with respect to fluid and particle properties, flow rates and geometry. Fluids are tested at different flow rates with and without rotation of drill string, with and without sand injection. This has allowed us to study the effects of flow rate and drill string rotation on hole cleaning capabilities of different fluids. The primary results are pressure drop, steady state sand bed height in a horizontal annulus versus fluid and cuttings rates for rotating and non-rotating drill string and in particular the critical rates for fully suspended flow. The results are interpreted in light of results from laboratory characterization of the same fluids, conducted as part of the same project. The results will increase understanding of the relationship between drilling fluid properties and hole cleaning performance. This will enable the development of improved drilling fluids, both operationally and environmentally. Such know-how will also be important in order to develop more accurate transport models.

Hole-cleaning performance comparison of oil-based and water-based drilling fluids

“…Results from the experimental investigation of oil-based fluids were reported (Sayindla et al, 2016). This paper presents comparative results of the oil-based and water-based fluids.…”

“…Also, rotation of drill string has a diminishing effect on Reynolds number at higher flow rates. Since we observe a significant effect of rotation on pressure gradient the Reynolds number definition used for our calculations is not sufficient to characterize the pressure gradient with rotation (Sayindla et al, 2016). Figure 9 presents the results from the experiments with continuous injection of sand particles.…”

Experimental Study of the Use of Tracing Particles for Interface Tracking in Primary Cementing in an Eccentric Hele–Shaw Cell

“…Length of the Cementing Section (l), m 500 1 Wellbore Size, in 16 As the radius ratio is r i /r o = 0.81 ≥0.3, it is acceptable to unwrap the annulus into a Hele-Shaw cell [14]. By assuming a standoff of 60% equivalent to 0.004 m distance between the casing and wellbore centers (d) (by using Equation ( 1)), the width and the variation of the gap by the width in the equivalent Hele-Shaw cell are calculated using Equations ( 5) and (6).…”

“…There are numerous numerical and experimental studies of the displacement flows of Newtonian and non-Newtonian fluids in annular geometries. Due to the problematic rheological behaviors of non-Newtonian fluids with and without yield-stress, there are fewer experimental studies about fluid flows in concentric and eccentric annular geometries with similarity to wellbore annulus in primary cementing [4][5][6][7][8][9][10][11][12][13][14][15][16]. In these limited experimental studies, it has been established that the type of flow (laminar, transition, and turbulent) [5,[10][11][12]17,18] and degree of eccentricity affect displacement efficiency significantly [19].…”

“…The frictional pressure drop and the relation between pressure drop and flow rate during the displacement flow of non-Newtonian fluids were described as well [4,10,11]. By using large-scale eccentric annular geometry, the importance of the rheological properties of the realistic non-Newtonian fluids for fluid flow and hole cleaning performance was expressed extensively [14][15][16], and the propagation of the fluid interfaces and displacement efficiency were characterized [24]. It was indicated that an enlarged irregular section, i.e., a washout causes an improvement in displacement in some scenarios in strongly inclined wellbores [17]; while being independent of the displacement efficiency in the washout itself, the presence of washouts may lead to poorer cement quality downstream of the washouts [23].…”