Due to the multifunctional effects of BSSSP on the reference fluid properties and according to its potential applicability, the interpretation of the findings was divided into three separate sub-sections, which are viscosity additive and filtration loss as well as partial loss treatment in the thief formations in order to understand the feasibility of using BSSSP in the petroleum industry.
Can BSSSP additives be utilized as a viscosifier in water-based drilling fluid?
Starting with the fresh conditions experimental findings, the effect of introducing 0.5% (3.5 gm), 1.5% (11 gm), 2.5% (18 gm), and 3.5% (24.5 gm) of BSSSP on the rheological characteristics of the drilling fluid was judged by comparing the measured values with the RF readings. The findings showed that BSSSP has a negligible impact on PV when compared to RF and no effect for the concentration variation was observed. However, BSSSP additives significantly increased the yield point; whereas 1.5% (11 gm) of BSSSP concentration increased YP by 400%; while 2.5% (18 gm) of BSSSP additive was less efficient than 1.5% (11 gm) of BSSSP and maximized YP by 357% when compared to RF. The 0.5% of BSSSP increased the YP by around 214%. In the same vein, increasing the concentrations of BSSSP also highly boosted the initial and final gel strengths when comparing them to RF and the effect of the concentration variation was almost insignificant. Figure 6 illustrates the impact of the three BSSSP concentrations on the rheological properties as compared to the reference fluid under fresh conditions. For 3.5% of BSSSP, there were no results as the liquid phase in the drilling fluid was not sufficient, the solids started to coagulate, and part of the additive was dry. In other words, the high concentration of BSSSP (3.5%) absorbed the free water, and a clotting phenomenon was experienced. In addition, the extreme reduction of pH caused the mud to fail for any measurement.
On the other hand, the aged conditions for 30 h and under 50 °C (122 °F) temperature had a positive impact on the rheological properties for the three concentrations of BSSSP when comparing them to the same concentrations of BSSSP under the fresh conditions. PV has increased by 63% for both concentrations of BSSSP (1.5% and 2.5%) and remained the same for 0.5%; while 0.5%, 1.5%, and 2.5% of BSSSP concentrations maximized YP by 18%, 35%, and 41%, respectively. Similarly, BSSSP additives considerably boosted the initial and final gel strengths under aged conditions. Moreover, 1.5% of BSSSP was more efficient than 2.5% of BSSSP in enhancing YP and gel strength, and there was no effect of the variation of the concentration on PV. Figure 7 shows the effect of the three BSSSP concentrations on the rheological properties under aged conditions (A.C) as compared to the three BSSSP concentrations under the fresh conditions (F.C).
Consequently, the three concentrations of BSSSP positively improved the rheological characteristics under both aged and fresh conditions. Additionally, experimental findings revealed that BSSSP was not affected by the aged time and temperature. The aged conditions reinforced the fluid rheology as compared to the fresh conditions. Furthermore, the results showed that a higher concentration of the BSSSP did not provide a proportionate enhancement in rheological properties. Hence, a lower concentration of 0.5–1% should be utilized as a viscosifier for optimal performance during normal drilling operations. As a result, the laboratory findings showed the possibility of utilizing BSSSP as a viscosity modifier. In other words, BSSSP has the capability to fulfill the same goals that conventional chemical additives can attain in the oilfield. Nevertheless, before BSSSP can be applied in the field, it should be examined under various pressures and temperatures using different aged times to assure that BSSSP is viable in the sub-surface conditions. Accordingly, more examinations should be executed under the wellbore conditions and hostile environment.
Can BSSSP be utilized as a seepage loss control material in water-based drilling fluid?
For the fresh conditions, LTLP filtration (75 °F and 100 psi) and HTHP filtration (250 °F and 500 psi) experiments were implemented for each concentration of BSSSP to precisely appraise the effect of 0.5%, 1.5%, and 2.5% additives on the seepage loss properties when juxtaposed to RF. It can be obviously observed that the filtration characteristics were enhanced for both LTLP and HTHP measurements when comparing to RF. Starting with LTLP findings, the filtrate (cc/30 min) was minimized by 22%, 24%, and 32% at 0.5%, 1.5%, and 2.5% BSSSP concentrations, respectively. Additionally, the filter cake thickness (mm/30 min) was remarkably decreased by 23%, 17%, and 34% at 0.5%, 1.5%, and 2.5% BSSSP concentrations, respectively. For HTHP filtration (250 °F and 500 psi) experiments, BSSSP was also efficacious in reinforcing the filtration properties; where HTHP filtrate was minimized by 25%, 27%, and 0.3% at 0.5%, 1.5%, and 2.5% concentrations of BSSSP, respectively. Similarly, mud cake thickness (mm/30 min) was notably improved by 15%, 13%, and 15% at 0.5%, 1.5%, and 2.5% concentrations of BSSSP, respectively. Figures 8 and 9 clarify the effect of the three BSSSP concentrations on seepage loss properties compared to RF under fresh conditions (LTLP and HTHP conditions). Once again, there were no results for the 3.5% of BSSSP for the same reason mentioned earlier.
The second part of this sub-section is related to the effect of aged conditions for 30 h and under 50 °C (122 °F) temperature on the performance and effectiveness of BSSSP. The aim is to closely simulate the wellbore conditions and to verify the efficiency of BSSSP additives on the filtration characteristics using a more hostile environment. The experimental results revealed that aged conditions boosted the seepage loss properties as juxtaposed to fresh conditions and for all the concentrations of BSSSP; where the LTLP fluid loss (cc/30 min) was reduced by 13%, 16%, and 12% at 0.5%, 1.5%, and 2.5% BSSSP concentrations, respectively. In addition, the mud cake (mm/30 min) was moderately reduced at 0.5% and 1.5% and it did not change at 2.5% BSSSP concentrations.
On the other hand, the HTHP filtration showed that the filtrate (cc/30 min) was decreased by 10%, 12%, and 15% at 0.5%, 1.5%, and 2.5% BSSSP concentrations, respectively. In addition, the filter cake thickness was also reduced for both concentrations of BSSSP (1.5% and 2.5%). Figures 10 and 11 elucidate the impact of the three BSSSP concentrations on the seepage loss properties under the aged conditions when comparing them to the same BSSSP concentrations under the fresh conditions (LTLP and HTHP conditions).
To sum it up, it can be observed that the three concentrations of BSSSP emphatically ameliorated the seepage specifications under aged and fresh conditions and for both LTLP and HTHP filtration. Moreover, the experimental findings showed that BSSSP was not impacted by the aging time and temperature. Contrarily, the aged conditions enhanced the filtration characteristics as juxtaposed to fresh conditions. Furthermore, the outcomes showed that higher concentration of the BSSSP had a small impact on enhancing the filtrate and filter cake thickness, accordingly a lower concentration of 0.5–1% should be utilized as a fluid loss control agent for optimal fulfillment during normal drilling operations. Plainly, BSSSP has the applicability to achieve the same targets as the conventional chemical additives used in the oilfield.
Can BSSSP additives be utilized as a partial loss treatment in the thief formations?
Lost circulation may also occur at any point in the drilling operation. If mud losses occur while drilling a long section of the well, the objective of the treatment will likely be to plug off or limit the losses to allow drilling to continue. In other situations, the goal may be to limit the losses and cement the well. Given sufficient experience in drilling a particular type of formation, it may be possible to avoid or significantly minimize lost circulation events by controlling mud properties, drilling rate, or other field parameters. However, this requires a high level of experience and study, which is generally not available. For this reason, the industry relies heavily on using methods of mitigating lost circulation events after they occur.
There are many lost circulation treatments used to stop or control mud loss. Plainly, the most common treatments that are used to control partial losses are high viscosity patch and lost circulation materials (LCM) such as granular, fibrous and flaky additives. Starting with high viscosity patch, this remedy is high viscosity drilling mud (patch) with low mud density. Ordinarily, the viscosity is maximized using lime, bentonite, or salt clay. In calculated and sufficient quantities, this pill is pumped in front of the thief zone, to plug the losses zone, especially in partial losses.
The marsh funnel viscosity for this pill is roughly 90–110 s. Moreover, one of the LCM can be used to combat the partial loss such as drilling mud (low density) plus one of the fibrous materials, drilling mud (low density) plus one of the granular materials, or drilling mud (low density) plus one of the flake materials. The experimental findings for aged and fresh conditions revealed that BSSSP had the feasibility to be utilized as a partial loss treatment; where all of Model 800 Viscometer, marsh funnel viscometer, and mud balance measurements provided a positive hint for BSSSP additives to be utilized for stopping partial loss. The goal of involving and discussing the mud weight in this sub-section is because all pills that are used to cease partial losses or any kind of mud loss should be low mud weight. The ultimate objective of having low mud weight pills is to avoid excessive equivalent circulation density in the annulus in front of the depleted formation and to prevent aggravating the problem. In return, unwanted consequences and side effects will be avoided (Basra Oil Company 2007).
For fresh conditions, concentrations of BSSSP had no impact on mud density; however, marsh funnel viscosity increased by 70%, 209%, and 191% at 0.5%, 1.5%, and 2.5% concentrations of BSSSP, respectively. Figures 12 and 13 illustrate the influence of the three BSSSP concentrations on the mud weight and marsh funnel viscosity properties as juxtaposed to RF under fresh conditions, respectively.
The aged conditions for 30 h and under 50 °C (122 °F) temperature for the three concentrations of BSSSP were investigated to guarantee BSSSP applicability under sub-surface conditions as compared to the same concentrations of BSSSP under fresh conditions. The experimental findings showed that aged conditions had no impact on the mud weight, and it had the same values as fresh conditions for all the concentrations. On the other hand, the laboratory outcomes exhibited that aged conditions effectively increased the marsh funnel viscosity when compared to fresh conditions and for all the concentrations of BSSSP; where marsh funnel viscosity increased by 11%, 5%, and 7% at 0.5%, 1.5%, and 2.5% BSSSP concentrations, respectively. Figures 14 and 15 demonstrate the effect of three BSSSP concentrations on mud weight and marsh funnel viscosity under aged conditions when comparing them to the same BSSSP concentrations under fresh conditions, respectively.
In summary, the three concentrations of BSSSP significantly improved marsh funnel viscosity under aged and fresh conditions and did not affect the mud weight. Additionally, the experimental results clarified that BSSSP was not affected by aging time and temperature. The aged conditions enhanced the marsh funnel viscosity when compared to fresh conditions. Moreover, the findings showed that a higher concentration of the BSSSP had a negative effect on the improvement of marsh funnel viscosity, and it had no impact on the mud weight. Accordingly, a concentration of 1.5–2% should be utilized for optimum performance to mitigate partial losses. Obviously, BSSSP has the possibility to accomplish the same aims that high viscosity pills can perform in the field in combating the partial losses.