Unconventional reservoir well production performance varies widely, even among wells in the same field. To improve drilling efficiency and reduce costs, operators need to acquire and conduct analysis of accurate reservoir information. In the Williston Basin, operators who collectively deployed the Halliburton CoreVault system were able to measure reservoir fluids more accurately and to leverage the regional value of this information, resulting in better production prediction, optimized oil recovery, and maximized economic value of their unconventional assets.
CHALLENGE
In today’s challenging economic conditions, oil and gas operators are relying on technology to mitigate and reduce risk for their projects. Many operators are engaged in innovative solutions to address the economic climate within the marketplace. To better understand this technical cooperation among operators, a look at both regulations and reservoir properties within the Bakken-Three Forks formation is necessary. In recent years, the North Dakota Industrial Commission enacted increased regulation for natural gas production and flaring.
In addition, operators acknowledged the critical importance of gas and oil property variations vertically between distinct reservoir horizons, and laterally within the field’s extent. Tighter regulations and economic constraints challenge operators to focus where they are drilling and accurately predict reservoir oil and gas production rates and volumes. Environmental and transportational safety of crude oils from North Dakota provided additional emphasis to the regional understanding of both oil and gas production practices and volumes.
SOLUTION
Unlike traditional logging and coring services that can allow 50 to 70% of fluids in the core to escape as they depressurize, the CoreVault tool utilizes pressure-tight containers to lock in 100% of the hydrocarbons in the core. This enables direct measurement of reservoir fluids so operators can avoid dry holes and accurately predict production.
The Halliburton CoreVault®Fluid and Rock Sampling system melds fluid sampling with rock coring, enabling fluid samples to be obtained from low-permeability reservoirs and preventing fluids from escaping during the acquisition of high-quality, rotary sidewall cores.
Accurate economic evaluation of a shale well previously required drilling and completing it. Traditional coring tools allowed fluids to escape from samples as they depressurized during retrieval.
As a result, analysis had to be based on estimates of fluids lost, rather than measurement of fluids in place. Also, conventional coring could take hours to days to retrieve just one core. The new Halliburton CoreVault system technology is changing all that. Built into the next-generation of the proven Hostile Rotary Sidewall Coring (HRSCT™) tool, the CoreVault system can capture up to 10 samples in a sealed container—in one run. The container prevents reservoir fluids from escaping during core retrieval and transport.
Traditional fluid sampling devices require the mobility of at least 0.01 mD/cp in order to pump moveable fluids from the rock into the sample chamber. The CoreVault system cuts high-quality cores, seals them in a pressure-tight container downhole, thus preserving the fluids in the cores. The sealed chamber can be transported to a laboratory under pressure at which time the reservoir fluids in those cores can be measured and analyzed.
In an unconventional field, operators can know a lot more – a lot sooner – about the size of the prize. The samples taken with the CoreVault system often reveal dramatically more oil and gas in place than previous estimates would indicate. The information obtained can significantly enhance economic value, and reduce exploration and development risks for operators.
RESULT
Halliburton collaborated with Bakken operators, who understand the value the CoreVault tool provides. They realized that, instead of each operator running its own coring operations, it would be more costeffective to collectively run these operations and to share the acquired data to more thoroughly map the Williston Basin region. The value of one well’s information is small in comparison to the knowledge gained from an understanding of the field.
By using CoreVault technology to gather cores strategically, operators are more informed regarding their own wells and have a clearer picture of what is occurring regionally. Operators have used this knowledge to optimize their production, drilling, and completion practices to maximize oil recovery, handle the gas properly, and maximize the oil that is shipped. While this arrangement is atypical, this sharing of knowledge and expertise to lower finding and development costs is reflective of the collaborative spirit necessary to achieve lower costs per BOE and succeed in these difficult times for the industry.
CoreVault® Fluid and Rock Sampling System
Maximum Temperature：400°F (204°C)
Maximum OD：6.00 in. (15.2 cm)
Length：32.31 ft (9.85 m)
Weight：960 lb (431 kg)
Maximum Pressure：25,000 psi (172,250 Kpa)
Minimum Hole：6.75 in. (17.4 cm)
Hardware：Tool Joints
Tension：100,000 lb(45,360 kg)
Compression：50,000 lb(22,680 kg)
Torque：600 lb-ft(815 N-m)
Case study
New technology improved targeting, reduced costs, and kept samples under pressure so hydrocarbons could be accurately measured.
An operator in Ohio and West Virginia used the system to retrieve 150 samples in five wells. Measurements of samples obtained with the CoreVault system showed 2.5 times more oil and gas in place than previously estimated. The operator also found variability in organic content, enabling better targeting and completion efficiency.
Previously, the operator estimated fluid loss from depressurized samples. Calculations, based on the faulty estimates, indicated an average of 78.2 scf/ton of hydrocarbons in the reservoir.
Samples retrieved by the CoreVault system revealed an average of 196.2 scf/ton. That meant the operator had 2.5 times more gas than expected. Thus, the CoreVault system enabled much more accurate valuation of gas in place. It also enabled better targeting because it retrieved multiple samples from different places along the wellbore.
Using conventional tools, the operator could have concluded that these wells would not be economic. But thanks to CoreVault system technology, the company knew the precise volume of oil and gas in the reservoir. The operator also obtained better information about where the most profitable zones were. That enabled the company to complete wells more efficiently and avoid fracturing nonprofitable zones and dry holes. Thus, CoreVault system technology contributed to more efficient use of capital.
石油圈
