LONDON, Jan 11 (Reuters) - Iraq, OPEC"s second-largest oil producer, will be able to boost exports by as much as 250,000 barrels per day (bpd) from the second quarter after finishing the installation of pumping stations at its Gulf ports, an Iraqi oil source said. The upgrade work explains why Iraq, which had long pumped above its OPEC production quota, has improved compliance with output targets over the past year, the source said. Upgrades would have prevented the country from pumping larger volumes. Iraq"s State Oil Marketing Organisation (SOMO) had exported as much as 3.7 million bpd from its southern ports in Basra, but the need to rehabilitate aging export infrastructure forced Iraq to reduce southern exports when upgrade work began from May 2020. The pandemic-driven slump in oil prices and tight Iraqi regulations resulted in delays to the projects, which were run by state-owned Basra Oil Co (BOC). Work to install new pumping stations to boost export capacity from Basra took place for most of 2021, an Iraqi oil ministry source told Reuters. Their start-up will increase Basra"s operational crude export capacity to 3.40 million-3.45 million bpd from 3.20 million bpd currently, with a target date of the second quarter, the source said. OPEC+ COMPLIANCE RISES The upgrade work coincided with efforts to improve Iraq"s compliance with OPEC+ output cuts, the source said. Iraq pledged in the second half of 2020 to boost compliance and compensate for previous overproduction after facing pressure from other OPEC+ members. Adherence rose in 2021 to average 97%, according to Reuters calculations based on OPEC figures. Iraq"s crude exports from Basra were close to reaching operational capacity in November and December last year at 3.195 million bpd and 3.180 million bpd respectively, according to SOMO figures seen by Reuters. The upgrade work will allow Iraq to increase exports as its OPEC+ quota rises, the oil ministry source said. It plans to boost southern export capacity to 6 million bpd by 2025. BOC also expects to complete maintenance operations to restore crude loading operations at the Khor al-Amaya port by the end of 2022, with an initial capacity of 400,000 bpd. read more