As you can read at the following article from Rudaw, the PKK does not accept the construction of a natural gas pipeline from Northern Iraq (Iraqi Kurdistan) to Turkey. Such a pipeline would necessarily have to pass from the Turkish Kurdistan too (see the map). The PKK is a Kurdish organization in Turkey, which is recognized as a terrorist organization by the US and Turkey, it is supported by Russia, and it has indeed carried out many terrorist attacks in Turkey. Rudaw is a Kurdish site from the Iraqi Kurdistan.
Map 1 Kurdistan
Many times I have referred to the Kurds, and their separation between the Kurds of Syria, Turkey and Iran, who are poor in oil and gas, and the Kurds of Iraq, who are very rich in oil and gas, and who need Turkey in order to export their oil and gas. The PKK is the big obstacle for the construction of a pipeline from Iraqi Kurdistan to Turkey, and that’s the reason there is now a war in East Turkey, between the Turkish government and the Kurds of Turkey (PKK).
“PKK official says group opposes KRG-Turkey natural gas agreement”, February 2016
“Turkey, Kurds in duel over energy”, February 2016