WEX Inc. said Tuesday that it has signed an agreement with Shell Oil Co. to process prepaid fuel card transactions for the petroleum giant’s commercial fleet operations in Europe and Asia.

The company did not disclose the value of the Shell contract, but in a news release, WEX President and CEO Melissa Smith called the deal “an exciting step in our long-term growth strategy.”

“We are thrilled that Shell has selected WEX as a prepaid fuel card processor,” Smith said.

Based in South Portland, WEX provides prepaid fuel cards and other payment services to businesses.

The company has been in growth mode in recent years, while continuing to expand its services into new industries.

In June, WEX announced plans to purchase Evolution1, a North Dakota-based technology firm in the health care sector that facilitates patient payments, for $532.5 million in cash. The deal, which would be the largest acquisition to date for WEX, is expected to close in the third quarter.

The planned acquisition marks another step in WEX’s ongoing diversification efforts after years of focusing exclusively on fuel payment solutions for companies with fleets of vehicles.

Over the past few years, WEX has begun offering payment-processing technology to health insurance providers and travel-related websites such as Expedia.com.

WEX is a publicly held company that trades on the New York Stock Exchange under the symbol WEX.

In trading Tuesday, its share price rose $2.37, or 2.24 percent, to close at $108.02 on news of the Shell contract.