Well MAID™ Paraffin Cleaning and Inhibition
with the Microbial Method in the Oilfield
In chemistry, paraffin is a term that can be used synonymously with “alkane”, indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the liquid phase past approximately 37 °C (99 °F).
Paraffin is a hydrocarbon compound that often precipitates on production components as a result of the changing temperatures and pressures within the production system. Heavy paraffin occurs as wax-like substances that may build up on the completion components and may, if severe, restrict production. Paraffin is usually found in the tubing close to the surface. Nevertheless, it can form at the perforations, or even inside the formation, especially in depleted reservoirs or reservoirs under gas-cycling conditions
In the microbial treatment, the proprietary nutrients are injected into the borehole to stimulate the growth of the specific beneficial natural occurring microbes. The metabolic process degrades the large molecules to the small ones so that the waxy paraffin molecules will be biologically degraded to short-chain organic molecules, which will be easier to flow, as demonstrated in Fig. 1. The growing microbial cultures not only clean the paraffin but also inhibit the formation of new paraffin.
Field Microbial Treatment Procedures:
The field microbial treatment procedure is not complicated but shall comply with the strict guidelines so that the microbial activities can be adequately stimulated. It is observed that ignorance of the importance of field treatment caused many failures in the field, such as shut-in the well for more than three months, but no symptom of production enhancement. The field microbial treatment procedure-Huff-and-Puff nutrients-is demonstrated in Fig. 2.
Selected Field Examples of Microbial Treatments:
The incremental production rate varies from one location to another. The effect of treatment is not just measured by oil production rate but by total liquid production rate plus the equivalent incremental gas volume. However, the operator only measures the effect in terms of the incremental total hydrocarbon production rate and ignore the water. According to our experience, the production rate enhancement can last for six months – more than two years. Unfortunately, not all of the operators will disclose the production data and detailed geology info to the service companies and allow us to publish it, so we have limited data to share.
Project 1: The depleted fractured vertical well has paraffin problem in Midland basin, Texas. The production well could not produce the whole day due to low daily liquid production rate. The operator reports paraffin issue in the borehole. Only 500 bbls nutrients were injected in the borehole in this pilot. More nutrients will be pumped in the next intervention, considering the existence of fractures.
Project 2: Microbial treatment of paraffin filled wells in Hutchinson County area of the Panhandle in Texas. This field started production in the 1940s. Most of the wells we treated were drilled in 1940s-1950s, its initial monthly production rate is 300-400 BOPM, the water production rate is 500-800 BWPM. After producing for several decades, these old wells were suffering the paraffin problems, which blocked the producer. Before the microbial treatment, the paraffin was removed by the scraper and adding some chemicals, which not only damages the downhole tools and could not remove the paraffin near the borehole wall. The chemicals will flow back to the surface immediately after resuming production. Therefore, the production enhancement is not significant and does last long, as shown in Fig. 4 (in the 3rd month). Afterward, the operator considered microbial treatment, which was more expensive than the traditional methods. However, as shown in Fig. 4 (in the 8th month), the production enhancement is significant, and last for almost two years, which means the operator does not need to repeat mechanical/chemical treatment of paraffin in this period. It also means that it not only cleans paraffin inside and near the borehole but also inhibit the formation of new paraffin. In the 30th month, the subject well was almost blocked by the paraffin. Then another microbial treatment is required.
Project 3: Microbial treatment of paraffin in Ohio State. The pay zone is sandstone formation. According to the laboratory analysis, the wax appearance temperature is 32℃(90℉), the wax content is high (>30%), the viscosity is 10.5 mPa×s. The API gravity is 30°. The daily oil production rates of the subject wells before the microbial treatment ranges from 0.5 BOPD to 1.5 BOPD, the water cut is above 98%. After the microbial treatment (shut-in for 7-10days), the daily oil production rate increased to 9.0-12.5 BOPD, the oil tube was cleaned, and the wax block disappeared. The percentage of production enhancement ranges from 400% – 2400%.