Hole Cleaning Performance of Light-Weight Drilling Fluids During Horizontal Underbalanced Drilling

Abstract

Hole cleaning is a major consideration at both the design and application stages of a drilling operation. If the fluid velocity is lower than a critical value at horizontal or high inclinations, a stationary bed develops which may cause various problems, such as high drag, higher probability of stuck pipe and higher hydraulic requirements, etc., if not removed properly. Therefore, this becomes important and essential to identifying critical velocity. This study aims to estimate the critical fluid-flow velocity for preventing the development of a stationary bed using empirical correlations that can be used easily at the field. Also, a rough estimation of bed thickness is introduced if the flow velocity is lower than the critical velocity. For this purpose, extensive cuttings transport experiments with water, called the Cuttings Transport Flow Loop, were conducted by the Petroleum and Natural Gas Engineering Department at Middle East Technical University (METU) in order to determine various inclinations, flow rates and rate of penetrations. The inner pipe is subject to a sagging, therefore more realistic annulus representation is achieved. Observations showed that a stationary bed can be developed even when the inclination of the wellbore is down to 50°. Results showed that the critical velocity could be estimated using the proposed correlations with reasonable accuracy when compared with the experimental results. Also, for flow velocities less than the critical values, the thickness of the stationary bed can be detected mostly within an error range of ±15%.

Review of Hole Cleaning in Complex Structural Wells

“…As shown in Table 2 and Table 3, even more factors such as mud rheology, cuttings concentration were considered in some correlations and models, complexity of cuttings transport leads to the big gap between theoretic studies and real drilling conditions. Therefore, steady layer models [51,55], transient models [32,[56][57][58][59][60], multi-region models [61,62], correlations [25,37,38,63] constantly appeared in the recent years.…”

“…Ozbayoglu et al [63] conducted extensive experiments to develop the empirical correlation for calculating estimate the critical velocity to prevent development of a cuttings bed. The inclination, ROP, annular size, mud viscosity and density were considered.…”

New mud for UnderBalanced Drilling

“…After mixing with the water and foaming, it is ready to apply in just few minutes. The density of the mud can be adjusted to drilling conditions in the range of 0.35-1.1 g/cm 3 . In its formula there are biodegradable anionic and amino polymers stabilizing the foam and simultaneously providing good technological parameters of the mud.…”

“…Air mud provides effi cient cuttings lifting and protection of producing formation. In view of this fact, it is often the most eff ective solution during drilling through the reservoir rock [1][2][3].…”

Overview Solids Transport Study and Application in Oil-Gas Industry-Theoretical Work

“…Once the solids deposition velocity, V crit is calculated, the cuttings concentration for a stationary bed (by true volume) in the annulus is calculated from (10) where Ozbayoglu et al (2010b) also conducted comprehensive flow loop tests with water at various deviation angles between 50°and 90°. The flow loop consisted of a 4Љ casing with 2Љ inner pipe 15ft in length.…”