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Technical Session on Well Integrity from Cementing Perspective & Solutions to Enhance Long-Term Zonal Isolation

Sprint organized a seminar for United Energy Pakistan Ltd. (UEPL) on Well Integrity from Cementing Perspective & the Solutions to Enhance the Long-Term Zonal Isolation in Karachi last September 18, 2019. We were delighted to have their Drilling and Completions Team during the session. The seminar was kick-started with a welcome note from our Regional Technical Manager, Mr. Hossam A. Elmoneim.

The technical resource speakers from Sprint were Mr. Kris Andre Looten and Mr. Rameez Anwar who emphasized the best practices for successful cementing jobs and Sprint's solutions in enhancing long-term zonal isolation. The speakers focused on addressing well integrity issues faced by operators within the region.

The seminar also provided our client with an exclusive insight into the CemMAX Technology which maintains a competent cement sheath over the well life. UEPL professionals actively interacted with our resource speakers and discussed their field case histories. Also present in the event from Sprint were Mr. Afnan Dar (Pakistan Country Operations Manager), Mr. Arif Yousuf (Principal Technical Engineer for Pakistan), Mr. Aziz Ur Rehman (Field Service Manager) and Mr. Adnan Fazal (PPS Team Lead).

Sprint's Recognition from ENI Pakistan

Sprint Oil and Gas Services was recognized by ENI Pakistan for its compliance with Eni’s HSE Standards during the 17th Contractors’ Senior Management HSE Workshop held at Marriott Hotel Karachi last April 11, 2019.

The recognition was presented by Mr. Angelo Ligrone, Managing Director for ENI Pakistan, and was accepted by Mr. Gufran Hameed Janjua - Sprint’s Senior QHSE advisor for Pakistan; he also delivered an HSE presentation during the event and engaged in a Q & A session.

The event was attended by ENI Management and representatives from the oil and gas services sector of Pakistan. Sprint’s delegation also included Mr. Arif Yousuf (Principal Technical Engineer) and Mr. Aziz Ur Rehman (Field Services Manager PPS).

Pakistan Oilfield Limited Jhandial-1 report on Pakistan Television

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Success Stories

Through Tubing Inflatable BP For Water Shutoff Leads to 43% Production Increase and 80% WC Reduction

The candidate well was a development well located in Khyber Pakhtunkhawa Province of Pakistan. It was completed as commingled gas condensate producer from Limestone (overlying) and Sandstone (underlying) formations. Well was brought online in 2010 and in 2013, PLT survey revealed 90% WC production from lower sandstone formations.

Initial attempts were made to set the blanking plug in the lower nipple profile with slickline to abandon the production from the lower zone. However, due to a damaged nipple profile the operation could not be completed.

Sprint recommended to set a TTIBP via CT in 7" Liner at 3,738 m, to isolate the water production from lower formation and to allow stimulating the upper Limestone formation with SRA-15 acid system.

Stimulation of Highly Fractured Limestone Reservoir Using NDA-S Non-damaging Diverting Acid Leads to a 30% Production Increase.

The Candidate was an appraisal well located in Khyber Pakhtunkhawa Province of Pakistan. The objective of the operator was to stimulate the upper limestone formation that was identified to have a high skin without the treatment to penetrate the lower producing formation.

The Well was a micro fractured high-pressure gas condensate producer and treatment fluid diversion was a key factor for uniform zonal coverage and job success. Additionally, the main challenge was the need to isolate the exposed lower sandstone formations prior to performing the treatment in the upper fractured limestone formation to avoid unpredictable deposition.

However, mechanical isolation could not be used due to a limitation in the nipple diameter. Accordingly, a treatment was designed to first place an NDP Non-Damaging Diverting Pill as a diverting platform across the lower sandstone formation then treating the main formation using SRA-15 and NDA-S (non-damaging diverter) to evenly stimulate the highly fractured limestone reservoir. The result was a 30% production increase.

Multi-Zone Stimulation Using Nitrified Alcoholic SRA-5 and SRA-15

The candidate well was a development well drilled in a Sindh oilfield in Pakistan. The well targeted three different gas producing zones each of these zones are separated by a packer and can be accessed through an SSD. The well was completed using a 5" tubing down to 2,588 m and with PBTD of 2,707 m.

The three producing zones were:

Zones Perf

interval (m)

WHFP (psi)

Zone -1

2315 - 2393.5

497

Zone - 2

2474 - 2567

579

Zone - 3

2588.5 - 2637

600

It was required to stimulate Zone-2 & Zone-3 and enhance its production by eliminating any formation damage. A matrix stimulation treatment using nitrified alcoholic SRA-15 proved to effectively increase the production of tight limestone and sandstone formations in wells with higher water affinity. An energized alcoholic SRA-15 treatment was used for stimulating two sandstone zones in the same well, resulting in unprecedented production enhancement with an increment of 3.7 folds in one zone and of 2.4 folds in the second, and total awarding production increment of 8.72 MMSCFD gas.

Tubing Patch Installation Using Straddle Packers and Coiled Tubing in Horizontal Wells

The candidate well was the second extended reach horizontal well in Pakistan. The well was drilled in Sindh province and had a horizontal departure to vertical depth ratio of more than 1.5. The main target of the well was (SML) formation and it was drilled as an 8 1/2'' hole and a 7'' liner was run and set at the depth of 1,700m leaving an OH section of 243m below liner shoe. A combination of 4-1/2'' and 5-1/2'' old tubing (above SSSV) were installed.

Well was later stimulated using Sprint's recommended SRA-15 and NDA-S systems and tested at 20 MMSCFD. During production, communication was observed in tubing annulus above SSSV, this was later confirmed using sonic logs to be at depth between 31.5m to 33.5m from RTKB

A "16 ft Tubing Patch" was installed above SSSV using a hydraulically set thru tubing straddle packers run on coiled tubing. The tubing patch successfully isolated the leak in the tubing and the job helped the production company to handle similar tubing damage without the need to pull the completion and loose well production.

Alcoholic SRA-15 Acid System Brings Back on Production Gas Well

The candidate well was a development well completed with a 7" Tie-back production liner down to 1,820 m and a 4.5" Liner from 1,758 m to 2,212 m. The well was producing from a carbonate cemented Sandstone formation through a perforated Interval from 1,846 m down to 2,166.5 m. The total net perforation interval was 197.5 m.

Due to low reservoir pressure (less than 500 psi), work-over on well was performed using inhibited OBM System and Nitrogen kickoff (s) were performed to bring back well on production. However, during well cleanout operation it was found that the bottom perforations were producing sand at a rate beyond surface separation facility capacity. Accordingly, it was decided to plug the bottom perforations using a bridge plug and to dump cement on top of it prior to performing a well stimulation job through Coiled Tubing. The plug was set at 2,101m and cement was dumped on top up to the depth of 2,103 m.

After the isolation of sand producing zone, the net perforated interval was reduced to +/-100m. And production reduced from 10 mmscf/day to merely 4.9 mmscf/day. A Matrix Stimulation treatment using SPRINT'S nitrified Organic Solvent and Alcoholic SRA-15 acid system in the sandstone reservoir resulted in a 60 % increase in production.

Sprint SRA-7.5 Used to Effectively Conduct Perforation Wash and Matrix Stimulation in Carbonate Cemented Sandstones

The well X-Deep-01 is an exploratory well drilled in Khyber Pakhtunkhwa and Mianwali District of Punjab, Pakistan. The well was spud on 18-Feb-2015 and drilled to 5669 m (18599 ft) to target Lumshiwal/Hangu (Sandstone) and Samanasuk/Shinawari (Limestone) Formations.

X-Deep-01 was producing from two different formations, the first was a carbonate cemented sandstone (Hungu/Lumshiwal) and the second was a Limestone  (Samanasuk/Shinawari). The client's objective was to stimulate the sandstone formation without causing sand deconsolidation. No stimulation was required for the Limestone (Samanasuk/Shinawari) since it had a negative skin.

The use of the weak SRA acid system with high loading of chelating agent helped the successful stimulation of the high carbonate content sandstone formation in the well X-Deep-01. Following the Stimulation job, the well production was increased by 20% yielding an oil production increase from 1200 to 1440 bbl and a 1.09 to 1.3 MMScf of gas per day.

Coiled Tubing Conveyed Perforations in Highly Deviated Well Increases Production by 80%

The candidate well is located in the second largest gas field in Sindh / Pakistan. Due to the limited height of the reservoir, most wells drilled in this field are highly deviated with an angle greater than 82º. This imposes a limitation on slick and wireline operations and typically requires the use of a worker rig to perform any production enhancement operation.

Due to the economic importance of the field and its major contribution into Pakistan overall gas production, it was requested by the client to bring up the production of the well at par with other producing wells.

22 meters of coiled tubing-conveyed hydraulically-operated perforations were performed over 4 runs. The use of coiled tubing helped overcoming the highly deviated well limitation and led to an 80% increase in production and an overall $850,000 operation saving to client. Tubing end locator helped correlating coiled tubing and wireline depths for an improved perforation depth accuracy.

Ultra Light-Weight HCS Cement Slurry Reduces Top Jobs Volume by 200%

The 26" hole was drilled in PILA SPI formation which is one of the weak formations in North Kurdistan. PILA SPI consists of a large section of limestone where severe losses are frequently observed during drilling with conventional mud systems. Under-balanced drilling technique is typically deployed in this section.

Sprint Ultra-lightweight high compressive strength slurry helped to reduce hydrostatic pressure of the fluid column and minimize the risk of lost circulation and ultimately sustain the integrity of the weak surface formations. The success in avoiding excessive losses helped minimize subsequent top jobs and provided excellent set cement properties to support the casing and isolate surface weak formations.

HCS Light-Weight GasTIGHT Cement Achieves Zonal Isolation Against Weak Gas Formation

The 8.5" hole section was drilled in BARSARIN formation, one of the weakest formation in Kurdistan. BARSARIN formation consists of intermixed limestone and sandstone layers where severe losses are typically encountered.

Being a production zone, the challenge was to avoid formation breakdown while controlling gas invasion to wellbore during cement placement. It was also, equally important to reduce gas migration potential during cement setting and to ensure zonal isolation between various sections.

It was also important to keep a tight control of the hydrostatic column of cement to fall within the narrow margin between the frac and pore pressures. Sprint Ultra-Lightweight high compressive strength GasTIGHT slurry helped maintaining weak formation integrity, avoiding excessive losses and preventing gas encroachment and ultimately providing excellent zonal isolation.

Wellbore Nitrified Acid Clean-out Using Rotary Jetting Tool in HT LP Environment

The concerned well is producing from a 14.5m of perforated interval through a 4.5" external upset CR-13-S-110 tubing completion with the production packer set at 9,902 ft. The well has a BHT of 340 ºF and a BHP of 2300 psi and the lower section of the hole is plugged back with a PBTD of 11,785'.

The complete field where the well was drilled, is suffering from several wellbore challenges, including sand flow back and tubing and perforations scaling due to produced formation water and reservoir pressure depletion. Moreover, when slick line operation was earlier conducted using a 1.8" slick line tool, the BHA could not reach BPTD depth and the maximum tagged depth was found to be 11,483 ft. Thus, a wellbore cleanout was required to restore well productivity and allow tools access to TD.

A nitrified SRA-10 acid treatment, pumped through a high pressure rotating jetting tool (SpinCAT) and placed underbalance, provided a technical and economical solution to wellbore scale cleanout in a high temperature low pressure environment and contributes to an incremental production of over 3 mmscf/day.

HP Jetting Tools Application in HT Scale Cleanout

Located in the foothills of the Himalayas, the well of concern exhibited a high temperature gradient leading to a BHT around 350 deg F. Meanwhile, the measured BHP was 2700 psi. As highlighted earlier, the produced water from the well had sufficient quantities of sulphates and carbonates along with Non-reactive ions like Barium and Strontium. Thus deposited scale created a hard structure that was difficult to remove with wireline bailers nor through drilling using through tubing motors and mills. Also, the dissolution of a recovered scale sample indicated that its solubility in HCl was limited to 15%. Finally, the client requested that any used solution should not cause sand deconsolidation or sand flowback.
 
Sprint optimized High Pressure Jetting Tool (HPJT) service helped cleaning 970 ft of hard sulfate and carbonate scale intermixed with sand particles using energized HCl based SRA-10 acid system. The cleanout helped restoring the well productivity and led to a 5.7 MMScf/day increase in gas production.

 

MaxOIL Diverts Acid Treatment Away From the Water-Zone in a Watered Out Pay-zone

Sprint MaxOil was pumped ahead of the HCl based SRA-15 main stimulation fluid to divert the treatment away from the water zone and into the oil bearing formation. The MaxOIL being a thin pumpable fluid that creates a rigid structure of gel once in contact with saline water, is used to effectively block water bearing formations. This allowed the main acid treatment to stimulate only the oil bearing formation.

The use of the MaxOIL led to an increase in oil production from 5% to 20% and a total increase in well productivity from ~1000 bpd to ~2500 bpd, This resulted in an oil production increase from 50 bpd to 500 bpd.

Publications

Novel Approach Towards The Field Application Of A Chelating Agent Based Stimulation System To Optimize DataFrac & Wellbore Stimulation In A Tight & Low Temperature Carbonate Reservoir

SPE-195665-MS, Presented at the PAPG/SPE Annual Technical Conference and Exhibition held in Islamabad, Pakistan, 10-12 December 2018.

In matrix acidizing of carbonate formations, acids are used to create wormholes that connect the formation to the wellbore. Hydrochloric acid, formic or acetic acid, or mixtures of these acids are commonly used in matrix acidizing treatments of carbonate reservoirs. However, the use of these acids exhibits some major limitations including high and uncontrolled reaction rate, face dissolution and corrosion to the completion goods, especially those made of chrome-based tubulars (Cr-13 and duplex steel), and these problems become severe at elevated temperatures. 

This paper presents a case study of a post datafrac operation wherein a state-of-the-art stimulation system, based on a chelating agent, is deployed in a matrix stimulation treatment of a low temperature tight carbonate reservoir for the first-time in the country. The new stimulation fluid allows the operator to optimize datafrac and wellbore stimulation in a single treatment. The approach also aids the project to be cost-effective and financially feasible, particularly in a low-budgetary environment.


Literature review comparing selected chelating agent and conventional acids is also described in this paper to support the approach adopted in abovesaid case study.

 

Improved Impact-Resisted Cement System Achieves the Side-Track in First Attempt in Complex Open Holes Environment Saving Four Folds of Operations Cost

SPE-195662-MS, Presented at the PAPG/SPE Annual Technical Conference and Exhibition held in Islamabad, Pakistan, 10-12 December 2018.

The operation of bypassing the existing borehole by placing a kick off cement plug has historically been very well established and long-standing technique. Although placement of a cement plug appears to be a routine and relatively simple job, the instances of kick off plug not fulfilling the desired purpose are quite frequent requiring same degree of planning as primary cement jobs. Traditional cement slurry systems for sidetracking have been focused on the development of compressive strength by reduced water content. These cements exhibit low resistance to impact and toughness requiring multiple attempts to side track the well. An industry average for kick-off plugs is 2.4 attempts per kick-off, with 24 hours rig time associated with each attempt.

This paper describes the engineered slurry system that incorporates unique properties of higher impact resistance, fracture toughness and load bearing capacity which resulted in slow ROP and sidetrack in 1st attempt. The main conclusion was supported by a field case study.

Production Optimization through Systematic Removal of Formation Damage, A Case Study of ENI Pakistan

SPE 15621, Presented at the SPE/PAPG Annual Technical Conference held in Islamabad, Pakistan, 22–23 November 2011.

Formation damage removal using matrix acid stimulation in Sandstone reservoir is recognized as a risky production optimization operation, however, a good understanding of formation mineralogy, root cause of formation damage, and stimulation procedures can help reduce the risk and increase the chance of success. The scope of this paper is to share Eni Pakistan’s workflow which lead to successful matrix acid stimulation campaigns in Bhit, Badhra and Kadanwari fields.

Prior to the damage removal operation, the selected wells’ deliverability analysis showed low productivity as compared to the ideal one. To restore the ideal wells’ productivity index, detailed damage analysis was performed

Seven candidate wells were selected for damage removal operation. The matrix stimulation operation resulted in incremental daily production of up to 160%. The increase in the production rate was accomplished by regaining the wells’ potential deliverability. This helped improve the fields’ reservoir management, accelerating hydrocarbon recovery and adding to the reserves.

Successful Approach of Scale Cleaning Using Organic Dissolvers To Delay Scale Re-Deposition at Pariwali Well # 5: A Case Study

SPE 142837, Presented at the SPE/PAPG Annual Technical Conference held in Islamabad, Pakistan, 10-11 November 2010.

Production drop caused by down hole scale deposition is a serious problem not only in wells producing with high water cut but also in deep, hot, sour gas wells with very low water cuts (trace to 6%).

This paper presents a case study of CaCO3 & CaSO4 scale deposition in a sour well in north of Pakistan that resulted in substantial production drop. HCl (15%) was used to dissolve/wash the scale obstruction in the tubular and clean the perforation of well. Although the treatment was successful in dissolving the scale and restoring the production, yet these production gains were lost rapidly. Scale dissolver treatments followed by scale inhibitions were also implemented but no appreciable results were achieved. A detailed in house study was carried out by POL for scale analysis and its removal techniques. Scale monitoring by produced water analysis, gauge cutter runs, production & WHFP fluctuations, gas analysis and review of seven scale cleaning jobs guided to carry out organic scale dissolving job.

Scale removal with organic dissolvers (Acetic acid) were recommended and proven successful because it maintained low pH which prevented re-precipitation of acid products. With this approach, scale re-deposition was delayed up to nine months.