Rice husk and saw dust as filter loss control agents for water-based muds

Abstract

When drilling with water based muds (WBM), significant fluid loss volumes from the mud into the formation can have adverse effects not just on the mud and its properties but also on the stability of the wellbore. Prevention of mud filter loss is one way of assessing the performance of a drilling mud. However, evaluation of the effectiveness or otherwise of a fluid loss control additive can be made by characterizing the mud cake formed. Interestingly, the mud cake characterization is one area that has been somewhat neglected in drilling fluid formulation with agro waste materials. Two cellulosic materials - rice husk and saw dust were chosen for the experimental study. The specie of the rice husk used was the African rice (Oryza glaberrima) while the dust from the saw milling of Oxystigma manni was utilized for this study. To ensure result acceptability, the rice husk and saw dust were ground and the resulting products were sieved to 1.25 × 10 −4 m. The filtration characteristics of the formulated mud samples were tested using the American Petroleum Institute (API) filter press and in accordance to the API recommended practice for field testing WBMs. From the filter loss tests, it was observed that the ground rice husk prevented filter loss by an average of 77% compared to ground saw dust filtration control of 63%. In addition, it was observed that at higher concentrations, ground saw dust and rice husk prevented fluid loss to the minimum acceptable API standard. For the filter cake thickness measured in millimetres, ground rice husk exhibited thicker mud cakes when compared with the saw dust by an average amount of 14%. For the mud cake characteristics, the rice husk mud exhibited smooth and slippery cakes while the saw dust mud exhibited rough texture, sticky and firm cakes.

Evaluating the locally sourced materials as fluid loss control additives in water-based drilling fluid

“…However, an increase in the content of the local additives in the drilling fluid samples indicated that there was a significant decrease in the filter loss volume results obtained from the mud samples. This result is attributed to the increase in cellulose content in the drilling fluid as the additive content increases (Agwu et al, 2019). The results as presented in Figure 11 depict that rice husk and Detarium microcarpum at 10g content was comparable with 2g CMC content in the drilling fluid sample, while 15g Brachystegia eurycoma content was comparable with the same CMC content.…”

“…Agwu and Akpabio (2018) added that drilling fluids are designed to reduce filtrate loss, form thin filter cakes that plaster the walls of the borehole to ensure minimal fluid loss and promote stability of the drilled well. As reported by Agwu et al (2019), the continuous fluid loss to the formation led to thick mud cake which in some cases resulted in pipe sticking, drag and torque problems, among others. Besides, Kosynkin et al (2011) mentioned that fluid invasion into porous media can damage reservoirs and reduce productivity by blocking hydrocarbon exit flow paths or causing wellbore collapse.…”

“…For the measurement of the qualitative characteristics of drilling fluid filter cake, Amanullah and Tan (2001) reported that there was no standard method to perform the evaluation rather it differs from researcher to researcher. Qualitatively, API describes drilling fluid filter cake as a firm, slippery, smooth, soft, sticky, etc (Agwu et al, 2019). Hence, from the appearance and texture of the formulated drilling fluid samples' filter cakes, the qualitative characteristics of the mud cake were established based on API description.…”

“…Hence, Eq. 3established by Lomba (2010) in Agwu et al (2019) was used to evaluate the formulated mud samples' mud cake permeability. Thus;…”

Formulation of cellulose using groundnut husk as an environment-friendly fluid loss retarder additive and rheological modifier comparable to PAC for WBM

“…Particles of a certain critical size stick at bottlenecks in the flow channels and form a bridge just inside the surface pores. Once a primary bridge is established, successively smaller particles are trapped, and thereafter, only filtrate invades the formation (Agwu et al 2019). These are known as bridging particles that are trapped in the surface of the pores while the finer particles, at first, are carried deeper into the formation.…”