Geochemistry of Formation Water and Implications for Ultradeep Tight Sandstone of DK Gas Field in Kuqa Depression

Table 1

The ion concentrations and pH values of different type formation water samples analyzed.

Sample ID	Type	Cl^- (mg/L)	SO4^2- (mg/L)	Ca^2+ (mg/L)	Mg^2+ (mg/L)	Na^+ (mg/L)	K^+ (mg/L)	TDS (mg/L)	pH
K-1	Condensate water	2200	10	171	23	1135	65	3603	3.7
K-2		181	16	9	0	127	2449	2782	7.0
K-3		3553	36	51	0	2965	547	7309	6.6
K-4		31	5	0	0	28	696	1157	7.0
K-5		972	11	78	12	446	46	1565	3.9
K-6		2646	0	196	19	1312	153	4326	4.5
K-7		271	92	6	2	168	90	629	7.3
K-8		24	2	3	0	11	27	68	7.4
K-9		33	31	4	1	16	13	96	5.0
K-10	Mixed water	4614	33	334	48	2386	186	7601	4.0
K-11		10437	239	771	95	5152	615	17309	4.0
K-12		6130	37	642	96	3205	803	11050	4.7
K-13		6277	87	449	54	3712	306	10885	4.3
K-14		20381		1555	236	9588	772	32532	3.7
K-15		15413	736	263	21	9834	1193	27631	6.4
K-16	Isolated formation water	156190	2350	14083	1264	85380	3549	262816	5.4
K-17		138145	290	8502	845	78562	3145	229503	4.8
K-18		181840	1950	19973	1342	95390	4284	304779	4.2
K-19		147630	0	10946	689	81820	3155	244240	3.8
K-20		182940	0	9237	631	109806	5184	310593	3.8
K-21		143171	595	12152	775	72289	4252	233234	5.0
K-22	Transition zone water	83145	790	7163	737	46147	1624	139606	6.9
K-23		92710	0	9308	650	48641	4872	156373	4.6
K-24		111710	275	8876	661	61970	3124	186691	5.6
K-25		116500	665	10335	697	62142	3773	194112	6.9
K-26		70460	1825	10435	712	33297	3520	120249	4.2
K-27		51935	705	2938	160	29162	2664	87564	7.2
K-28		86405	385	8702	1185	43943	5656	146276	4.4
K-29		105510	2870	9976	1350	51302	5698	176706	4.8
K-30		106470	2130	9888	668	57065	3547	179768	6.8

The content of HCO₃^- and CO₃^2- are very low and the detection error is large, so they are not listed. TDS: total dissolved solids.