Experimental Investigation of Foam drilling fluid using Visualization Technique

Abstract

Cutting transport is one of the major factors, which affects the cost, time and quality of drilling operations. Over the years, as the number of directional wells have increased to improve the productivity, it has been observed that cutting transport is more difficult in horizontal and directional wells as compared to vertical wells. While the foam/aerated drilling fluid provides significant advantages over conventional drilling fluid such as higher rate of penetration and reduction in formation damage, however these advantages are reduced due to inefficient cutting transport to the surface. This study investigates the effect of different parameters such as cuttings weight concentration, liquid flow rate and gas flow rate on cutting transport using foam/aerated drilling fluid. The experiments were conducted in a 6.16 m long horizontal pipe with 2.5 in. inner diameter and 4.5 in. outer diameter and annular diameter ratio of 1.8. The liquid and the gas flow rate was varied between 219 - 380 kg/min and 4 - 6.5 L/min, while the gas input pressure was kept constant at 2 bar. An anionic surfactant was used to stabilize the foam with a stationary liquid density of 818 kg/m3. The concentration of the borosilicate solid glass beads of 2-3 mm average diameter was varied between 0 - 4 wt. %. The results showed that increase in the liquid flow rate or Reynold number improved cutting transport, whereas increase in the gas flow rate and solid cuttings concentration decreased the cutting transport velocity for a constant gas input pressure. A non-dimensional performance parameter was introduced, for comparison of the cutting transport efficiency of different fluids such as water, 0.05 wt. % and 0.1 wt. % bio-polymer concentrations. It was observed that foam fluid has the highest bed height, Reynold number and lowest solid velocity (Reynold number). Performance parameter indicates that foam fluid has a better cutting transport efficiency as compared to bio-polymer based drilling fluid for horizontal drilling. This study can act as a guide to improve our knowledge of cutting transport and how cutting transport efficiency of different fluids can be compared using performance parameter.